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Flexible binary phase photon sieves on polyimide substrates by laser ablation

Mool Gupta, Matthew Julian, and David Macdonnell

Doc ID: 326554 Received 21 Mar 2018; Accepted 17 Apr 2018; Posted 18 Apr 2018  View: PDF

Abstract: Binary phase diffractive optical element photon sieve is fabricated by direct laser ablation of a thin, flexible polyimide substrate with a nanosecond-pulsed ultraviolet (UV) laser. The binary phase photon sieve operates at 633 nm and was designed with 19 rings and a focal length of 400 mm. The total time to fabricate the photon sieves were tens of seconds. Surface properties of the laser-processed areas are examined, and optical performance of the photon sieve is characterized and compared to FDTD simulations. By optimizing the laser fluence and travel distance between laser pulses, features with sub-wavelength surface roughness were achieved. The photon sieve showed good focusing ability with suppressed side-lobes. When the fractional area of photon sieve pinholes was made to approach 50%, the binary sieve diffraction efficiency approached 11%; matching the highest value reported in the literature for a photon sieve. Thus, this work demonstrates both high efficiency, lightweight diffractive optics suitable for space satellite and other applications, with capabilities for low cost and high throughput fabrication.

Thermo-optic soliton routing in nematic liquid crystals

Armando Piccardi, Ula Laudyn, Michal Kwasny, Miroslaw Karpierz, and Gaetano Assanto

Doc ID: 322957 Received 13 Feb 2018; Accepted 16 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: We demonstrate thermo-optic control on the propagationof optical spatial solitons in nematic liquid crystals.By varying the sample temperature, both linearand nonlinear optical properties of the reorientationalmaterial are modulated by acting on the refractive indices,the birefringence and the elastic response. Asa result, both trajectory and transverse confinement ofspatial solitons can be adjusted, demonstrating an effectivemeans to tune and readdress self-induced opticalwaveguides.

Controllable coherent backscattering of light in disordered media filled with liquid crystal

Jose Trull, Marc Cuevas, Josep Salud, Crina Cojocaru, and David López

Doc ID: 326070 Received 14 Mar 2018; Accepted 16 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: We have investigated multiple scattering of light in a disordered system based on liquid crystals for a temperature-controllable random laser. Coherent backscattering measurements at several temperatures have been well fitted by the theoretical model deduced for a random collection of spherical point scatters based on a diffusion approximation. The transport mean free path exclusively depends upon the diffusivity of the liquid crystalline phase of the hybrid scattering system. It is shown how the laser threshold excitation intensity is strongly correlated with the transport mean free path.

Resonance-domain diffractive lens for the terahertz region

Christian Nadell, Kebin Fan, and Willie Padilla

Doc ID: 325272 Received 02 Mar 2018; Accepted 15 Apr 2018; Posted 16 Apr 2018  View: PDF

Abstract: Diffractive optics have long served as the basis of spectroscopicmeasurements of materials. Operation inthe resonance domain further allows these elements toachieve high efficiency and polarization control. Effectivemedium theory is a practical tool for modelingsuch optics, and here we extend use of this theory tothe terahertz (THz) region, experimentally demonstratingan all-dielectric binary off-axis diffractive lens. Weachieve a high efficiency, polarization independent opticwhich both focuses and disperses THz light, suggestingpotential applications in pharmaceutical, security,and semiconductor imaging

Out-of-plane band structure of a two-dimensional dispersive photonic crystal

Jesús Valenzuela-Sau and Raul Garcia-Llamas

Doc ID: 325983 Received 13 Mar 2018; Accepted 13 Apr 2018; Posted 16 Apr 2018  View: PDF

Abstract: We calculated the out-of-plane band structure of a two-dimensional photonic crystal (PC). To achieve this goal, the Plane Wave Expansion Method (PWEM) was implemented in conjunction with a novel numerical algorithm; the Dispersive Photonic Crystal Iterative Method (DPCIM). The PC is a circular cross section dispersive MgO Lorentz single-pole rods in square lattice. The frequency bands are calculated starting at Γ as function of the oblique component of the wave vector; γ. For the lowest frequencies, it was found that the modes bend drastically to the horizon as the dielectric constant, ɛ(ω), is increased to a very positive value. For frequencies above the longitudinal optical phonon circular frequency, where ɛ(ω) has very low positive values, the modes show a low dispersive behavior, the expected degeneration occurs in the transparency window, ɛ (ω) ~1, and a line of modes behave close to the line of light.

Spectroscopic properties and continuous wave deep-red laser operation of Eu3+-doped LiYF4

Maxim Demesh, Anatol Yasukevich, Viktor Kisel, Alexei Kornienko, Elena Dunina, Valentin Orlovich, Vladimir Dashkevich, Elena Castellano-Hernández, Christian Kraenkel, and Nikolai Kuleshov

Doc ID: 326022 Received 14 Mar 2018; Accepted 13 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: Eu3+-doped LiYF4 is reexamined as a laser material for the visible spectral region. Polarized absorption and emission cross sections as well as the fluorescence lifetime are determined. Branching ratios and radiative lifetime are calculated within the theory of 4f-4f transition intensities which takes into account the influence of an excited configuration of the opposite parity 4fN-15d. CW laser operation at 702 nm is demonstrated with a maximum output power of 15 mW and a slope efficiency of 4.6% under pumping with a frequency doubled Ti:sapphire laser at 393.5 nm.

Experimental demonstration of beacon-less beam displacement tracking for an orbital-angular-momentum-multiplexed free-space optical link

Long Li, Runzhou Zhang, Guodong Xie, Yongxiong Ren, Zhe Zhao, Zhe Wang, Cong Liu, haoqian song, Kai Pang, Robert Bock, Moshe Tur, and Alan Willner

Doc ID: 325093 Received 05 Mar 2018; Accepted 12 Apr 2018; Posted 18 Apr 2018  View: PDF

Abstract: In this letter, we experimentally demonstrate beacon-less beam displacement tracking for a free-space optical communication link multiplexing multiple orbital-angular-momentum (OAM) beams, where the data-carrying OAM beams themselves are used for position detection. In our demonstration, 400-Gbit/s data transmission is achieved under emulated lateral displacement of up to ±10 mm with power penalties of less than 3 dB for all channels. Channel crosstalk is reduced by the beam tracking system to below -18 dB. Moreover, we investigate using a Gaussian-beacon for beam displacement tracking, and achieve similar channel crosstalk and power penalties compared with using the beacon-less beam tracking.

Intrinsic bias in Fisher Information calculations formulti-mode image registration

David Tyler

Doc ID: 324849 Received 28 Feb 2018; Accepted 12 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: To address the need for quantitative analysis of imageprocessing and optical requirements in multi-modeimaging systems, such as multi-spectral and polarimetricimagers, I have developed a Fisher Information matrixto quantify errors in estimating the shift betweentwo images with non-transformational feature differences.If images of same field have differences not attributableto a geometric transformation, uncertainty inestimating the parameters of the transformation willbe increased by intrinsic bias; or bias inherent in thedata itself, as opposed to bias originating in the estimationalgorithm. The approach to shift-estimation erroranalysis described in this Letter accounts for intrinsicbias, has intuitively-expected properties, and givenplanned system sensitivity and operating conditions,can be used with simulated imagery to bound imageregistration error and develop realistic requirements.

Raman Scattering Enhancement of a Single ZnO Nanorod Decorated with Ag Nanoparticles: Synergies of Defects and Plasmons

Ruibin Lin, Liang Hu, Jinzhang Wang, Wenjing Zhang, Shuangchen Ruan, and Yujia Zeng

Doc ID: 326030 Received 14 Mar 2018; Accepted 11 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: Surface enhanced Raman scattering (SERS) of a single ZnO nanorod (NR) is demonstrated by coating with Ag nanoparticles (NPs). An enhancement factor of 4.4×102 and 3.9×101 has been obtained for E2 (high) mode (437cm-1) and A1 (TO) mode (378 cm-1), respectively. Electron paramagnetic resonance (EPR) measurements reveal an unintentional donor state in ZnO NRs. The enhancement of deep-level emission and micro-absorption mapping of a single ZnO NR further confirm the presence of the donor state. The SERS is believed to result from the charge transfer (CT) between ZnO NRs and Ag NPs, which can be enhanced by the empty donor state in ZnO. Finally, single ZnO NRs coated with Ag can be used as good SERS substrates for R6G molecules. This study highlights the interaction between point defects and SERS effect down to a single semiconductor NR.

Transition of Fabry-Perot and antiresonant mechanisms via a SMF-Capillary-SMF structure

Xiaobei Zhang, Haiyang Pan, Huawen Bai, Ming Yan, Jiawei Wang, Deng Chuanlu, and Tingyun Wang

Doc ID: 325885 Received 12 Mar 2018; Accepted 10 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: In this paper, we investigate the transition of the well-known Fabry-Perot (FP) and antiresonant (AR) mechanisms via a single mode fiber (SMF)-capillary-SMF structure. The critical length for this transition is analytically found as a linear relation with the capillary inner diameter based on the ray optic method, which shows the agreement with both numerical simulations and experiments. Evolutions of the transmission and reflection spectra verify that FP and AR mechanisms are close related to the critical length. Observed AR envelope modulated by the FP mechanism in the reflection strengthens gradually with the increase of the capillary length, which is expected to be a novel method for potential applications in multi-parameters sensing because of its combined mechanisms. The transition and critical length can be also found and explained using the same method in other types of AR fibers or waveguides with a hollow core.

Wideband tunable optoelectronic oscillator based on microwave photonic filter with ultra-narrow passband

Haitao Tang, Yuan Yu, Ziwei Wang, Xu Lu, and Xinliang Zhang

Doc ID: 326254 Received 20 Mar 2018; Accepted 10 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: A novel wideband tunable optoelectronic oscillator based on microwave photonic filter (MPF) with ultra-narrow passband is proposed and experimentally demonstrated. The single passband MPF is realized by cascading a MPF based on the stimulated Brillouin scattering and an infinite impulse response (IIR) MPF based on active fiber recirculating delay loop. The measured full width at half maximum bandwidth of the cascaded MPFs is 150 kHz. To the best of my knowledge, this is the first time to realize such a narrow passband in single passband MPF. The oscillation frequency of the OEO can be tuned from 0 to 40 GHz owing to the wideband tunability of the MPF. Thanks to the ultra-high mode selectivity of the IIR filter, the mode hopping is successfully suppressed. A stable microwave signal at 8.18 GHz is obtained with phase noise of -113 dBc/Hz at 10 kHz and the side mode noise is below -95 dBc/Hz. The signal-to-noise ratio exceeds 50 dB during the tuning process

Universal holonomic single quantum gates over a geometric spin with phase-modulated polarized light

Naoki Ishida, Takaaki Nakamura, Touta Tanaka, Shota Mishima, Hiroki Kano, Ryota Kuroiwa, Yuhei Sekiguchi, and Hideo Kosaka

Doc ID: 325683 Received 16 Mar 2018; Accepted 10 Apr 2018; Posted 16 Apr 2018  View: PDF

Abstract: We demonstrate universal non-adiabatic non-abelian holonomic single quantum gates over a geometric electron spin with phase-modulated polarized light and 93% average fidelity. This allows purely geometric rotation about an arbitrary axis by any angle defined by light polarization and phase using a degenerate three-level Λ-type system in a negatively-charged nitrogen-vacancy center in diamond. Since the control light is completely resonant to the ancillary excited state, the demonstrated holonomic gate is not only fast with low power, but also precise without the dynamical phase being subject to control error and environmental noise. It thus allows pulse shaping for further fidelity.

Photon statistics as an interference phenomenon

Thomas Mehringer, Simon Mährlein, Joachim von Zanthier, and Girish Agarwal

Doc ID: 320069 Received 31 Jan 2018; Accepted 10 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: Interference of light fields, first postulated by Young in 1801, is one of the fundamental pillars of physics. Dirac extended this observation later to the realm of the quantum world by stating that each photon interferes only with itself. A precondition for interference to occur is that no welcher-weg information labels the paths the photon takes, otherwise the interference vanishes. This remains true even if two-photon interference is considered as, e.g., in the Hong-Ou-Mandel-experiment. Here, the two photons interfere only if they are indistinguishable in frequency, momentum, polarization and time.Less known is the fact that two-photon interference and photon indistinguishability also determines the photon statistics in the overlapping light fields of two independent sources.As a consequence, measuring the photon statistics in the far field reveals the degree of indistinguishability of photons emitted by independent sources. In this letter, we first prove this statement theoretically using a quantum mechanical treatment. We then demonstrate the result with a simple experimental setup consisting of two statistically independent thermal light sources with adjustable polarizations. We find that the photon statistics varies indeed as a function of the polarization settings, the latter determining the degree of welcher-weg information of the photons emanating from the two sources.

Dielectric-mirror-less femtosecond optical parametric oscillator with ultrabroad-band tunability

Jintao Fan, CHENGLIN Gu, Jun Zhao, Ruoyu Liao, Yuxi Chu, Lu Chai, Qingyue Wang, and Ming-lie Hu

Doc ID: 320777 Received 01 Feb 2018; Accepted 09 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: We demonstrate a high average power, widely tunable, dielectric-mirror-less optical parametric oscillator (OPO) based on MgO:PPLN, which is synchronously pumped by a 1040 nm femtosecond fiber laser. The OPO does not require any dielectric coating mirrors. By exploiting the four-prism-sequence-system combined with the gold mirrors, the oscillating laser pulses could span the spectral regions both in the signal and idler, the outputpulses of OPO can be tuned across 1367—1914 nm in the signal, and 2152—4480 nm in the idler as well. This device can deliver as much as 1.2 W of average power at 1482 nm in the signal and up to 411 mW at 3487 nm inthe idler, respectively. The ultrabroad-band spectra tunability, along with the high average output property makes the dielectric-mirror-less OPO an attractive alternative to the conventional OPOs.

Microwave photonics instantaneous frequency measurement receiver based on Sagnac Loop

Hossein Emami, Mohammadreza Hajihashemi, Sayyed Alavi, and abu sahmah m supa'at

Doc ID: 323487 Received 19 Feb 2018; Accepted 09 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: A microwave photonics instantaneous frequency measurementreceiver was conceived and practicallydemonstrated. The systems is based on phase modulationinside a Sagnac loop and therefore needs nobias voltage resulting in no DC bias drifts. The systemprovides a DC output whose amplitude is a function of input RF signal and thus no high-frequency photo-detector is required. Furthermore, the system exhibits a very good sensitivity without the aid of any sort of electrical noise cancellation techniques such as lock-in amplification. This makes the system response faster which would be another benefit for electronic warfare applications. Less than 6% measurement error was achieved over a 0.01-40 GHz frequency range for -30 dBm RF level. Also, a -51 dBm sensitivity was obtained accepting a 10% error.

Surface plasmon resonance sensing in gaseous media with optical fiber gratings

Alvaro Gonzalez-Vila, Andreas Ioannou, Médéric Loyez, Marc Debliquy, Driss Lahem, and Christophe Caucheteur

Doc ID: 324990 Received 01 Mar 2018; Accepted 09 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: Surface plasmon resonance excitation with optical fiber gratings has been typically studied in aqueous solutions. This work describes the procedure to excite a plasmon wave in gaseous media and perform refractive index measurements in these environments. Grating photo-inscription with 193 nm excimer laser radiation allows to obtain slightly tilted fiber Bragg gratings exhibiting a cladding mode resonance comb along several hundreds of nm. Their refractive index sensitive range extends from gases to liquids, so operation in both media is compared. We demonstrate that the thickness of the metal coating required for surface plasmon excitation in gases is roughly one third of the one usually used for liquids. The developed platforms exhibit a temperature insensitive response of 78 nm/RIU when tested with different gases.

Photonic analog-to-digital conversion using red frequency chirp in a quantum-dot semiconductor optical amplifier

Motoharu Matsuura, Takuya Okada, and Hiroki Hoshino

Doc ID: 325203 Received 01 Mar 2018; Accepted 09 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: A photonic analog-to-digital conversion (PADC) based on intensity-to-frequency conversion using frequency chirp in a quantum-dot semiconductor optical amplifier (QD-SOA) is proposed. The presented PADC has a simple scheme whereby optical quantization is achieved using a single QD-SOA, with multiple rectangular bandpass filters placed in parallel. In this work, we successfully achieve 10-GSamples/s, 8-level optical quantization using a QD-SOA. The PADC also has much lower input signal pulse power requirements for optical quantization, compared with conventional PADCs.

Lineshape-asymmetry elimination in weak atomic transitions driven by an intense standing wave field

Dionysis Antypas, Anne Fabricant, and Dmitry Budker

Doc ID: 325248 Received 15 Mar 2018; Accepted 09 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: Owing to the ac-Stark effect, the lineshape of a weak optical transition in an atomic beam can become significantly distorted, when driven by an intense standing wave field. We use an Yb atomic beam to study the lineshape of the 6s2 1S0 → 5d6s 3D1 transition, which is excited with light circulating in a Fabry-Perot resonator. We demonstrate two methods to avoid the distortion of the transition profile. Of these, one relies on the operation of the resonator in multiple longitudinal modes, and the other in multiple transverse modes.

Compact, circular, and optically stable multipass cell for mobile laser absorption spectroscopy

Manuel Graf, Bela Tuzson, and Lukas Emmenegger

Doc ID: 326235 Received 16 Mar 2018; Accepted 09 Apr 2018; Posted 18 Apr 2018  View: PDF

Abstract: Compact and lightweight laser absorption spectrometers for accurate trace gas measurements are of great scientific and commercial importance. In these instruments, the multipass cell (MPC) represents a critical element in terms of achievable size and sensitivity. Herein, we introduce a versatile MPC-concept that unifies compactness, mechanical rigidity, and optical stability. Relying on fundamental cavity design principles and modern diamond turning techniques, we have developed a segmented circular MPC allowing efficient and interference-free beam folding. A protoype cell is presented that features up to 10 m optical path length at a total mass of less than 200 g. Incorporated in a highly compact setup without any beam pre-shaping optics, we demonstrate a normalized noise level of low 10-⁴ (2σ) at 1 Hz.

Fabrication and optical properties of Pr3+ doped Ba (Sn, Zr, Mg, Ta) O3 transparent ceramic phosphor

Zicheng Wen, Chaoyang Ma, chong zhao, Fei Tang, Zhijun Cao, Zhiquan Cao, xuanyi yuan, and yongge cao

Doc ID: 326511 Received 30 Mar 2018; Accepted 09 Apr 2018; Posted 18 Apr 2018  View: PDF

Abstract: A novel transparent ceramic phosphor of Pr3+ doped Ba (Sn, Zr, Mg, Ta) O3 (Pr3+: BMT) were successfully fabricated via high temperature solid-state reaction method. The in-line transmittance of 59% at 650 nm was measured. The Pr3+: BMT ceramic phosphor can emit 650nm red light excited by 447nm blue light. The ceramic phosphor can still work at 383K. The activation energy was calculated to be 0.17 eV. The efficiency of the ceramic phosphor is twice as much as that of its powder phosphor. The Pr3+: BMT ceramic phosphor showed good thermal stability and enhanced the chromaticity of its white LEDs, which make it a promising red phosphor for lighting.

Exact calculation of the nonlinear characteristics of 2D isotropic and anisotropic nonlinear slot waveguides

Mahmoud Elsawy and Gilles Renversez

Doc ID: 325569 Received 08 Mar 2018; Accepted 09 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: We use our vector Maxwell’s nonlinear eigenmodesolver to study the stationary solutions in 2D cross-section plasmonic slot waveguides with isotropic andanisotropic Kerr nonlinear cores. First, for the isotropiccase, we demonstrate that, even in the low powerregime, 1D studies may not provide accurate and meaningful results compared to 2D ones. Second, we studyincluding at high powers the link between the nonlinear parameter γ nl and the change of the nonlinear propagation constant ∆β. Third, we demonstrate that our approach is also valid for anisotropic waveguides, and we show how to improve by a factor two the figure of meritof nonlinear plasmonic slot waveguides using realisticmaterials.

High-power, continuous-wave, tunable mid-IR, higher-order vortex beam optical parametric oscillator

A. Aadhi, Varun Sharma, and Goutam K. Samanta

Doc ID: 325665 Received 08 Mar 2018; Accepted 09 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: We report on a novel experimental scheme to generate continuous-wave (cw), high power, and higher-order optical vortices tunable across mid-IR wavelength range. Using cw, two-crystal, singly resonant optical parametric oscillator (T-SRO) and pumping one of the crystals with Gaussian beam and the other crystal with optical vortices of orders, lp = 1 to 6, we have directly transferred the vortices at near-IR to the mid-IR wavelength range. The idler vortices of orders, li = 1 to 6, are tunable across 2276–3576 nm with a maximum output power of 6.8 W at order of, li = 1, for the pump power of 25 W corresponding to a near-IR vortex to mid-IR vortex conversion efficiency as high as 27.2%. Unlike the SROs generating optical vortices restricted to lower orders (≤2) due to the elevated operation threshold of SRO with higher order pump vortices, here, the coherent energy coupling between the resonant signals of two crystals of T-SRO facilitates the transfer of pump vortex of any order to the idler wavelength without stringent operation threshold condition. The generic experimental scheme can be used in any wavelength range across the electromagnetic spectrum and in all time scales from cw to ultrafast regime.

Dispersion Tuning in Sub-Micron Tapers for Third Harmonic and Photon Triplet Generation

Jonas Hammer, Andrea Cavanna, Riccardo Pennetta, Maria Chekhova, Philip Russell, and Nicolas Joly

Doc ID: 325649 Received 08 Mar 2018; Accepted 09 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: Precise control of the dispersion landscape is of crucial importance if optical fibers are to be successfully used for generation of three-photon states of light – the inverse of third harmonic generation. Here we report gas-tuning of intermodal phase-matched third-harmonic generation in sub-micron-diameter tapered optical fiber. By adjusting the pressure of the surrounding argon gas up to 50 bar, intermodally phase-matched third harmonic light can be generated for pump wavelengths within a 15 nm range around 1.38 µm. We also measure the infrared fluorescence generated in the fiber when pumped in the visible and estimate that the accidental coincidence rate in this signal is lower than the predicted detection rate of photon triplets.

A 45 fs Diode-Pumped Yb:CALGO Laser Oscillator With 1.7 MW of Peak Power

Arkady Major and Sujith Manjooran

Doc ID: 326251 Received 16 Mar 2018; Accepted 09 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: A high power sub-50 fs diode-pumped Yb:CALGO laser oscillator was demonstrated. The peak power achieved for 45 fs pulses directly from the oscillator was 1.7 MW. We believe that this is the highest peak power in the sub-50 fs pulse regime that was ever produced directly from any diode-pumped Yb-ion-doped laser oscillators to date. The shortest generated pulses were 38 fs long with 187 kW of peak power.

Refractive index sensing by Brillouin scattering in side-polished optical fibers

Romeo Bernini, Gianluca Persichetti, Ester Catalano, Luigi Zeni, and Aldo Minardo

Doc ID: 320437 Received 24 Jan 2018; Accepted 09 Apr 2018; Posted 12 Apr 2018  View: PDF

Abstract: In this paper, we demonstrate the possibility to measure the refractive index of a liquid, using the stimulating Brillouin scattering in a 3cm-long side-polished optical fiber. In addition, we show that, depositing a high-refractive index layer on the polished surface, the sensitivity of the Brillouin frequency shift (BFS) can be increased thanks to a higher penetration of the evanescent field in the outer medium. Experiments show a maximum BFS change of about 11 MHz when varying the refractive index of the external medium from 1 (air) to 1.402, and a BFS sensitivity to refractive index of about 293 MHz/RIU around 1.40.

1.8mJ, 3.5kW single frequency optical pulses at 1572nm generated from an all-fiber MOPA system

Wangkuen Lee, Jihong Geng, Shibin Jiang, and Anthony Yu

Doc ID: 321046 Received 31 Jan 2018; Accepted 09 Apr 2018; Posted 12 Apr 2018  View: PDF

Abstract: High energy single frequency optical pulses at 1572nm were generated from an all-fiber MOPA system for atmospheric CO2 LIDAR system application. We report experimental demonstration of 1.8mJ, peak power of 3.5kW at the pulse repetition of 2.5 kHz, as well as 1.3mJ, peak power of 2.5kW at the pulse repetition of 7.5 kHz single frequency optical pulses at 1572nm using single-mode large core polarization maintaining Er-Yb co-doped silicate glass fiber amplifiers pumped at 976nm. To our best knowledge, this is the highest pulse energy of single frequency at 1572nm from an all-fiber amplifier system.

Photoluminescence enhancement in metallodielectric-capped non-polar ZnO films

YONGHUI ZHOU, Shanshan Chen, Xinhua Pan, and Zhizhen Ye

Doc ID: 322570 Received 06 Feb 2018; Accepted 09 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: Non-polar ZnO thin films were grown on m-plane sapphire substrates by plasma-assisted molecular beam epitaxy. Emission enhancement from non-polar ZnO thin films coated with Al/AlOx has been studied by photoluminescence spectroscopy. AlOx has been used to mediate the surface plasmons (SPs) energy of Al nanoparticles. Taking advantage of the resonant coupling between UV emission of non-polar ZnO film and Al nanoparticle SPs, a 84-fold enhancement of the UV emission and a 8.3-fold enhancement of internal quantum efficiency (ηint) have been achieved under the optimized sputtering time and energy of SPs.

Controlling the Degree of Polarization of Partially Coherent Electromagnetic Beams with Lenses

Taco Visser, Govind Agrawal, and Xinying Zhao

Doc ID: 324583 Received 20 Feb 2018; Accepted 08 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: We show theoretically that the degree of polarization of a partially coherent electromagnetic beam changes dramatically as the beam is being focused. A low numerical aperture lens can considerably enhance the degree of polarization at its geometrical focus. When two identical lenes are employed in a 4f configuration, the degree of polarization of a beam can be tailored by using amplitude masks in the Fourier plane located in the middle of the two lenses. Our findings open up the possibility to control this fundamental property of random beams in a simple manner.

Partially coherent sources with radial coherence

Gemma Piquero, Massimo Santarsiero, Rosario Martinez-Herrero, Juan Carlos de Sande, Massimo Alonzo, and Franco Gori

Doc ID: 325575 Received 07 Mar 2018; Accepted 08 Apr 2018; Posted 13 Apr 2018  View: PDF

Abstract: Partially coherent sources with radial coherence are proposed. They present a circularly symmetric intensity profile and a degree of coherence whose absolute value only depends on the angular difference between the two considered points. In particular, the source is completely coherent at pairs of points belonging to the same radius. The modal structure of such sources is determined in the general case, and conditions are derived under which the field propagated in paraxial approximation remains radially coherent at any transverseplane.In such cases, the angular dependence of the correlation function is preserved upon propagation, although the intensity profile generally changes.An example of this kind of sources has been experimentally synthesizedby means of a simple set up and its coherence characteristics have been tested by means of a Young interferometer.

Charge compensation effects of Yb3+ on the Bi+: near-infrared emission in PbF2 crystal

Peixiong Zhang, Nan Chen, Rui Wang, Xingbin Huang, Siqi Zhu, Zhen Li, Hao Yin, and Zhenqiang Chen

Doc ID: 326283 Received 19 Mar 2018; Accepted 08 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: The used of Yb3+ codoping for enhancing the near infrared (NIR) emission in Bi, Yb codoped PbF2 crystal was investigated for the first time, to the best of our knowledge. The NIR and visible fluorescence emission properties of the as-grown crystals were investigated in details. It is found that the Yb3+ ion can act as an effective charge compensated ion to bring about the conversion from Bi2+ to Bi+, enhancing the NIR fluorescence emission in Bi:PbF2 crystal. Moreover, the NIR fluorescence emission peaking at around 1090 and 1485 nm were demonstrated to be two different Bi+ related centers, Bi(I) and Bi(II), respectively. These results suggest that Bi, Yb codoped PbF2 crystal may become an attractive gain material for developing NIR broadband lasers under the pump of different wavelengths.

Sparsity-Based Reconstruction for Super-Resolved Limited-View Photoacoustic Computed Tomography Deep in a Scattering Medium

David Egolf, Ryan Chee, and Roger Zemp

Doc ID: 324989 Received 08 Mar 2018; Accepted 07 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: Delay-and-sum beamforming (DSB) of photoacoustic data does not incorporate a priori spatial sparsity of the imaging target. By incorporating this information into beamforming for limited-view photoacoustic computed tomography, we experimentally obtained enhanced resolution images of wires at a depth of 8.5 mm in a tissue mimicking scattering medium. Using a 21 MHz transducer, we improved resolution from the 200-250 μm achieved by DSB to 75 μm. After applying smoothing, the full width at half maximum (FWHM) of the sparsity-based technique was roughly 25 μm and 10 μm in the lateral and axial directions, much smaller than the 180 μm and 120 μm lateral and axial FWHM's of DSB.

In Vivo Time Gated Diffuse Correlation Spectroscopy at Null Source-Detector Separation

Marco Pagliazzi, Sanathana Konugolu Venkata Sekar, Laura Di Sieno, lorenzo colombo, Turgut Durduran, Davide Contini, Alessandro Torricelli, Antonio Pifferi, and Alberto Dalla Mora

Doc ID: 321030 Received 12 Feb 2018; Accepted 07 Apr 2018; Posted 18 Apr 2018  View: PDF

Abstract: We demonstrate time domain diffuse correlation spectroscopy at null source-detector separation by using a fast time-gated single-photon avalanche diode (SPAD) without the need of a time-tagging electronics. This approach allows for increased photon collection, simplified real time instrumentation and reduced probe dimensions. Depth discriminating, null-distance measurement of blood flow in a human subject is presented. We envision the miniaturization and integration of matrices of optical sensors of increased spatial resolution and the enhancement of the contrast of local blood flow changes.

Two-pole microring weight banks

Alexander Tait, Allie Wu, Thomas Ferreira de Lima, Mitchell Nahmias, Bhavin Shastri, and Paul Prucnal

Doc ID: 319497 Received 29 Jan 2018; Accepted 07 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: Weighted addition is an elemental multi-input to single-output operation that can be implemented with high-performance photonic devices. Microring weight banks bring programmable weighted addition to silicon photonics. Prior work showed that their channel limits are affected by coherent inter-channel effects that occur uniquely in weight banks. We fabricate two-pole designs that exploit this inter-channel interference in a way that is robust to dynamic tuning and fabrication variation. Scaling analysis predicts a channel count improvement of 3.4-fold, substantially greater than predicted by incoherent analysis used in conventional microring devices. Advances in weight bank design expand the potentials of reconfigurable analog photonic networks and multi-channel microwave photonics.

A new auto-focus and reconstruction method based on connected domain

Haiyan Ou, Wu Yong, Edmund Lam, and Wang Bing-Zhong

Doc ID: 318868 Received 05 Jan 2018; Accepted 06 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: In this letter, we propose a new method for autofocusing and reconstruction without defocus noise in optical scanning holography. By using connected domain (CD) to calculate the area of different domains, which are labeled by connected component (CC), the focus distance can be found via certain criteria. Meanwhile, the sectional images without defocus noise can also be reconstructed based on the labeled domains. The effectiveness of this method has been verified with simulation and experiments.

Parallel sorting of orbital and spin angular momenta of light in record large number of channels

Gary Walsh, Luciano De Sio, David Roberts, Nelson Tabiryan, Francisco Aranda, and Brian Kimball

Doc ID: 326151 Received 15 Mar 2018; Accepted 06 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: Parallel sorting of orbital and spin angular momentum components of structured optical beams is demonstrated. Both spin channels are multiplexed within the novel orbital angular momentum sorter reducing size, weight, and number of elements. Sorted states are linearly spaced over 70 topological charge values. We experimentally and theoretically evaluate operational range and crosstalk between neighboring channels and find 30 orbital angular momentum states are available per spin channel for quantum communication or cryptography. This is achieved using an angular momentum sorter we developed based on geometric phase optical elements. We present two devices consisting of liquid crystal polymer films photoaligned with complex two-dimensional patterns. The components show 96% diffraction efficiency.

Chemical elemental analysis of single acoustic-levitated water droplets by laser-induced breakdown spectroscopy

Victor Contreras Loera, Ricardo Valencia, Jairo Peralta, Hugo Sobral, Marco Antonio Meneses-Nava, and Horacio Martinez

Doc ID: 324870 Received 27 Feb 2018; Accepted 05 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: Laser Induced Breakdown Spectroscopy is presented for trace element detection of liquid samples by analyzing a single droplet levitated by ultrasonic waves. A single liquid droplet is placed in the node of a standing acoustic wave produced by a uniaxial levitator for further chemical analysis. The acoustic levitator consists on a commercial Langevin type transducer, attached to a concave mechanical amplifier, and a concave reflector. A micro-syringe was used to manually place individual liquid droplet samples in the acoustic levitation system. For chemical analysis, a laser-induced plasma is produced by focusing a single laser pulse on the levitated water-droplet after it partially dries. The performance of the acoustic levitator on micron-size droplets is discussed and the detection of Ba, Cd, Hg and Pb at ppm (mg/L) and sub-ppm levels is reported. The process, starting from placing the sample in the acoustic levitator and ending on the chemical identification of the traces, takes few minutes. The approach is particularly interesting in applications demanding limited volumes of liquid samples and relative simple and inexpensive techniques.

Focusing Short-Wavelength Surface Plasmons by a Plasmonic Mirror

Erdem Ogut, Cenk Yanik, Ismet Kaya, Cleva Ow-Yang, and Ibrahim Sendur

Doc ID: 325714 Received 09 Mar 2018; Accepted 05 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: Emerging applications in nanotechnology, such as super-resolution imaging, ultra-sensitive biomedical detection, and heat-assisted magnetic recording require plasmonic devices that can generate intense optical spots beyond the diffraction limit. One of the important drawbacks of surface plasmon focusing structures is their complex design, which is significant for ease of integration with other nanostructures and fabrication at low-cost. In this study, a planar plasmonic mirror is investigated that can focus surface plasmons to produce intense optical spots having lateral and vertical dimensions of λ/9.7 and λ/80, respectively. Intense optical spots beyond the diffraction limit were produced from the plasmonic parabolic mirror by exciting short-wavelength surface plasmons. The refractive index and numerical aperture of the plasmonic parabolic mirror were varied to excite short-wavelength surface plasmons. Finite-element method simulations of the plasmonic mirror, and scanning near-field optical microscopy experiments have shown very good agreement.

Nonlinear pulse compression based on a gas-filled multipass cell

Loïc Lavenu, Michele natile, Florent Guichard, Yoann Zaouter, Xavier Delen, Marc Hanna, Eric Mottay, and Patrick Georges

Doc ID: 324809 Received 23 Feb 2018; Accepted 05 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: We demonstrate nonlinear temporal compression of a high energy Yb-doped fiber laser source in a multipass cell filled with argon. The 160 µJ 275 fs input pulses are compressed down to 135 µJ 33 fs at the output, corresponding to an overall transmission of 85%. We also analyze the output beam, revealing essentially no space-time couplings. We believe this technique can be scalable to higher pulse energies and shorter pulse durations, enabling access to a wider parameter range for a large variety of ultrafast laser sources.

Phase-Dependent Laser Acceleration of Electrons with Symmetrically Driven Silicon Dual Pillar Gratings

Kenneth Leedle, Dylan Black, Yu Miao, Karel Urbanek, Andrew Ceballos, Huiyang Deng, James Harris, Olav Solgaard, and Robert Byer

Doc ID: 320534 Received 25 Jan 2018; Accepted 05 Apr 2018; Posted 05 Apr 2018  View: PDF

Abstract: We present the demonstration of phase-dependent laser acceleration and deflection of electrons using a symmetrically driven silicon dual pillar grating structure. We show that exciting an evanescent inverse Smith-Purcell mode on each side of a dual pillar grating can produce hyperbolic cosine acceleration and hyperbolic sine deflection modes, depending on the relative excitation phase of each side. Our devices accelerate sub-relativistic 99.0 keV kinetic energy electrons by 3.0 keV over a 15 μm distance for accelerating gradients of 200 MeV/m with 40 nJ, 300 fs, 1940 nm pulses from an optical parametric amplifier. These results represent a significant step towards making practical dielectric laser accelerators for ultrafast, medical, and high energy applications.

Strong Confinment of Optical Fields using Localized Surface Phonon Polaritons in Cubic Boron Nitride


Doc ID: 322634 Received 14 Feb 2018; Accepted 05 Apr 2018; Posted 05 Apr 2018  View: PDF

Abstract: Phonon polaritons (PhPs) are long-lived electromagnetic modes that originate from the coupling of infrared photons with the bound ionic lattice of a polar crystal. Cubic-Boron nitride (cBN) is such a polar, semiconductor material, which due to the light atomic masses can support high frequency optical phonons. Here, we report on random arrays of cBN nanostructures fabricated via an unpatterned reactive ion etching process. FTIR reflection spectra suggest the presence of localized surface PhPs within the Reststrahlen band, with quality factors in excess of 38 observed. These can provide the basis of next generation infrared optical components like antennas for communication, improved chemical spectroscopies, and enhanced emitters, sources and detectors.

Observation of an Optical Spring With a Beamsplitter

Jonathan Cripe, Baylee Danz, Benjamin Lane, Mary Lorio, Julia Falcone, Garrett Cole, and Thomas Corbitt

Doc ID: 314774 Received 09 Jan 2018; Accepted 03 Apr 2018; Posted 05 Apr 2018  View: PDF

Abstract: We present the experimental observation of an optical spring without the use of an optical cavity. The optical spring is produced by interference at a beamsplitter and, in principle, does not have the damping force associated with optical springs created in detuned cavities. The experiment consists of a Michelson-Sagnac interferometer (with no recycling cavities) with a partially reflective GaAs microresonator as the beamsplitter that produces the optical spring. Our experimental measurements at input powers of up to 360 mW show the shift of the optical spring frequency as a function of power and are in excellent agreement with theoretical predictions. In addition, we show that the optical spring is able to keep the interferometer stable and locked without the use of external feedback.

A fast and robust standard-deviation based method for bulk-motion compensation in phase-based functional OCT

Xiang Wei, Acner Benech, Shaohua Pi, William Cepurna, David Huang, John Morrison, and Yali Jia

Doc ID: 320185 Received 22 Jan 2018; Accepted 03 Apr 2018; Posted 05 Apr 2018  View: PDF

Abstract: Phase-based optical coherence tomography (OCT), such as OCT angiography (OCTA) and Doppler OCT, is sensitive to the confounding phase shift introduced by subject bulk motion. Traditional bulk motion compensation methods are limited by their accuracy and computing cost-effectiveness. In this paper, we present a novel bulk motion compensation method for phase-based functional OCT. Bulk-motion associated phase shift can be directly derived by solving its equation using standard deviation of phase-based OCTA and Doppler OCT flow signals. This method was evaluated on rodent retinal images acquired by a prototype visible-light OCT and human retinal images acquired by a commercial system. The image quality and computational speed were significantly improved, compared to two conventional phase compensation methods.

Measurement of differential modal group delay of a fewmode fiber using Fourier Domain Mode Locked laser

Deepa Venkitesh, Varun Kelkar, and Smaranika Swain

Doc ID: 323324 Received 16 Feb 2018; Accepted 03 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: We propose and experimentally demonstrate a methodfor measuring the differential modal group delay(DMGD) of a few mode fiber using a Fourier domainmode-locked laser (FDML). We use the fast frequency-swept,wavelength-tunable output of the FDML in orderto perform time domain measurements of interferenceof the modes, which is further post processed toextract the DMGD. We demonstrate the measurementof DMGD for a commercial two-mode fiber over the C-band.This method is not limited by the magnitude ofDMGD and the number of modes and is minimally affectedby time-dependent polarization and mode fluctuations,environmental noise and spectral resolution ofinstruments.

Quadrature detection for self‐mixing interferometry

Junfeng Wu and Fengfeng Shu

Doc ID: 324878 Received 01 Mar 2018; Accepted 03 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: We establish a new quadrature detection system for self‐mixing interferometry using two photodiodes and a 22.5 degrees rotated beam splitter. The method is based on a rotating beam splitter placed between the laser diode and measured object, and two quadrature self-mixing signals can be obtained. Then an arctangent phase algorithm can be used to demodulate the quadrature signal to acquire the object vibration information. This method simplifies the self-mixing signal demodulation process and allows demodulate the vibrating displacement more easily. Experimental results demonstrate the feasibility of quadrature detection for self-mixing optical measurement. This Letter provides guidance for the design of self‐mixing interferometers.

An integrated all-optical programmable logic array based on semiconductor optical amplifiers

Dong wenchan, Zhuyang Huang, Jie Hou, Rui Santos, and Xinliang Zhang

Doc ID: 325021 Received 05 Mar 2018; Accepted 03 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: All-optical programmable logic array (PLA) is one of the most important optical complex logic devices, which can implement combinational logic functions. In this Letter, we propose and experimentally demonstrate an integrated all-optical PLA at the operation speed of 40 Gb/s. The PLA mainly consists of a delay interferometer (DI) and semiconductor optical amplifiers (SOAs) of different lengths. The DI is used to pre-code the input signals and improve the reconfigurability of the scheme. The longer SOAs are nonlinear mediums for generating canonical logic units (CLUs) using four-wave mixing (FWM). The shorter SOAs are used to select out the appropriate CLUs by changing the working states, then reconfigurable logic functions can be output directly. Results show that all the CLUs are realized successfully and the optical signal-to-noise ratios are above 22 dB. The exclusive NOR gate and exclusive OR gate are experimentally demonstrated based on output CLUs.


Stéphane Clemmen, Alessandro Farsi, Sven Ramelow, and Alexander Gaeta

Doc ID: 325117 Received 01 Mar 2018; Accepted 02 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: We demonstrate a photon buffer for quantum communication systems via a quantum frequency-conversion-dispersion technique based on Bragg scattering four-wave mixing. The all-fiber setup is capable of imparting all-optical and continuously tunable delays onto single photons with minimal photon noise and absorption. Tunable delays up to times the photon duration are demonstrated with on/off efficiencies as high as 55%.

FSI-based non-cooperative target absolute distance measurement method using PLL correction for the influence of a nonlinear clock

Cheng Lu, Xiang Yong, Gan Yu, Liu Bingguo, chen fengdong, Liu guodong, and liu xiaosheng

Doc ID: 315038 Received 07 Dec 2017; Accepted 02 Apr 2018; Posted 03 Apr 2018  View: PDF

Abstract: We propose a frequency swept interferometry (FSI)-based absolute distance measurement method that can be used to measure a non-cooperative target located at a distance of tens of meters. In this method, an external cavity laser serves as the frequency tuning laser, and a single frequency laser and two acoustic optical modulators (AOMs) are used to measure the optical path difference (OPD) variation during the frequency tuning, which can correct the Doppler effect. A phase-locked loop (PLL) is introduced to synchronize the nonlinearities between the OPD variation measurement signal and the absolute distance measurement signal, improving the signal-to-noise ratio (SNR) of the OPD variation measurement signal. The distance to a non-cooperative target located at 15 m is experimentally measured using this method, and a precision of 3.43 μm is obtained.

Coherence Distance in Indoor Optical Wireless Communication Channels

Dima Bykhovsky

Doc ID: 325894 Received 15 Mar 2018; Accepted 02 Apr 2018; Posted 11 Apr 2018  View: PDF

Abstract: The coherence distance (CD) is the spatial distance over which the channel does not change appreciably. It is a common and important wireless communication channel parameter. While adoption of this parameter in the realm of radio-frequency (RF) is well established, it is a less familiar concept in the realm of optical wireless communication (OWC), where it can be beneficial as a measure for spatial optical channel changes. In this letter, the average coherence distance is proposed as a metric to characterize indoor OWC channels and a method for its evaluation is outlined.

Wide dynamic range high-speed three-dimensional quantitative OCT angiography with hybrid-beam scan

Taejin Park, Sun-Joo Jang, Myounghee Han, Sukyoung Ryu, and Wang-Yuhl Oh

Doc ID: 324790 Received 23 Feb 2018; Accepted 01 Apr 2018; Posted 05 Apr 2018  View: PDF

Abstract: We demonstrate a novel hybrid-beam-scanning-based quantitative optical coherence tomography angiography (OCTA) that provides high-speed wide dynamic range blood flow speed imaging. The hybrid-beam scanning scheme enables multiple OCTA image acquisitions with a wide range of multiple time intervals simultaneously, providing wide dynamic range blood flow speed imaging independent of the blood vessel orientation, which was quantified over a speed range of 0.6 mm/s ~ 104 mm/s through the blood flow phantom experiments. A fully automated high-speed hybrid-beam-scanning-based quantitative OCTA system demonstrates visualization of blood flow speeds in various vessels from main arteries to capillaries in 4 mm x 4 mm area (1024 A-lines x 512 B- scans) in vivo in 20 seconds, showing its potential as a useful imaging tool for various biomedical applications.

Angular momentum switching and orthogonal fieldconstruction of C-points

B.S.Bhargava Ram, Ruchi ., and Paramasivam Senthilkumaran

Doc ID: 322953 Received 09 Feb 2018; Accepted 31 Mar 2018; Posted 03 Apr 2018  View: PDF

Abstract: In this letter, we take up the non-trivial problem oftransforming a C-point singularity into its orthogonalstate by switching its angular momentum components.For homogeneous distribution, orthogonal transformationis a trivial operation of using a single halfwaveplate (HWP). For C-point singularity, this entailschange in the handedness without disturbing the index,followed by rotation of state of polarizations in thedistribution. Swapping the spin angular momentum(SAM) components of C-point singularities leads to indexand handedness inversion. Switching of orbital angularmomentum (OAM) components of C-point can bemade to result only in handedness inversion. We showhere, by changing the SAM and OAM components insequence a C-point can be transformed into its orthogonalstate. While experimentally demonstrating this, wealso show that a spiral phase plate, which is a phaseelement can also perform polarization transformationoperation.

Single-beam spectrally encoded color imaging

Mitsuhiro Ikuta, DongKyun Kang, Dukho Do, Adel Zeidan, and Guillermo Tearney

Doc ID: 325340 Received 05 Mar 2018; Accepted 31 Mar 2018; Posted 11 Apr 2018  View: PDF

Abstract: We have developed a new method of conducting spectrally-encoded color imaging using a single light beam. In the new method, a single broadband light beam was incident on a diffraction grating, where the overlapped 3rd order of the red, 4th order of the green, and 5th order of the blue spectral bands were focused on a line illuminating tissue. This configuration enabled each point on the line to be illuminated by three distinctive wavelengths, corresponding to red, green, and blue. A custom grating was designed and fabricated to achieve high diffraction efficiencies for the wavelengths and diffraction orders used for color spectrally-encoded imaging. A bench system was built to test the new spectrally-encoded color imaging method. For a beam diameter of 174 µm, the bench system achieved 89,000 effective pixels over a 70º circular field. Spectrally-encoded color images of excised swine tissue revealed blood vessels with a similar color appearance to those obtained via a conventional color camera. Results suggest that this single-beam spectrally-encoded color method is feasible and can potentially simplify color spectrally-encoded endoscopy probe designs.

Phase imaging and synthetic aperture super-resolutionvia total internal reflection microscopy

Guillaume Maire, Hugues Giovannini, Anne Talneau, Patrick Chaumet, Kamal Belkebir, and Anne Sentenac

Doc ID: 321235 Received 06 Feb 2018; Accepted 31 Mar 2018; Posted 05 Apr 2018  View: PDF

Abstract: Total internal reflection microscopy is mainly used inits fluorescence mode, and is the reference technique toimage fluorescent proteins in the vicinity of cell membranes.Here, we show that this technique can easilybecome a phase microscope by simply detecting the coherentsignal resulting from the interference betweenthe field scattered by the probed sample and the totalinternal reflection. Moreover, combining several illuminationangles permits to generate synthetic aperturereconstructions with improved resolutions compared tostandard label-free microscopy techniques.

Multimilliwatt, tunable, continuous-wave, mid-infrared generation across 4.6-4.7 μm based on orientation-patterned GaP

Kavita Devi, Anuja Padhye, Peter Schunemann, and Majid Ebrahim-Zadeh

Doc ID: 319865 Received 16 Jan 2018; Accepted 30 Mar 2018; Posted 11 Apr 2018  View: PDF

Abstract: We report the generation of tunable continuous-wave (cw) mid-infrared (mid-IR) radiation across 4608-4694 nm using the new nonlinear material, orientation-patterned gallium phosphide (OP-GaP). By exploiting difference-frequency-mixing between a cw Tm-fiber laser and a home-built cw optical parametric oscillator in a 40-mm-long crystal, we have generated up to 43 mW of cw output power, with >30 mW across >95% of the mid-IR tuning range. The output at 4608 nm exhibits high beam quality, with a passive power stability of 2.5% rms over 1.5 mins. The temperature acceptance bandwidth of the OP-GaP crystal has been measured and compared with theory. The performance of the mid-IR source at high pump powers and polarization-dependent transmission in OP-GaP has been investigated.

Higher-order cladding mode excitation of fs-laser inscribed tilted-FBGs

Andreas Ioannou, Antreas Theodosiou, Kyriacos Kalli, and Christophe Caucheteur

Doc ID: 325968 Received 13 Mar 2018; Accepted 30 Mar 2018; Posted 05 Apr 2018  View: PDF

Abstract: We study the modal behaviour of plane-by-plane femtosecond laser fabricated tilted fibre Bragg gratings (TFBGs). The focus is made on the differential strain and temperature sensitivities between the cladding mode resonances of a nth grating order and those of the (n-i)th orders (with i=1–n), which are collocated in the same wavelength range. Whereas the Bragg mode exhibits an axial strain sensitivity of 1.2 pm/με, we experimentally show that the strain sensitivity of ultra-high order cladding modes is negative and at -1.99 pm/με in the same spectral window. Using a finite element mode solver, the modal refractive index value is computed to be well below 1, thus confirming that these modes are in reality leaky modes.

Dual-channel operation in a synchronously-pumped optical parametric oscillator for generation of broadband mid-infrared coherent light sources

Zhaowei Zhang, Pei Liu, Puyuan He, and Sicong Wang

Doc ID: 326730 Received 23 Mar 2018; Accepted 29 Mar 2018; Posted 05 Apr 2018  View: PDF

Abstract: We report a novel approach for generating broadband mid-infrared (mid-IR) light by implementing a dual-channel scheme in a synchronously-pumped OPO (SPOPO). Two-channel operation was achieved by inserting a prism-pair and two reflection-mirrors inside an OPO cavity. Pumped by a Yb: fiber laser, the OPO generated an idler wave at ~3150 nm with a -10-dB bandwidth of ~13.2 THz, which was twice as much as that of the pump source. This scheme represents a promising technical route to transform conventional SPOPOs into a device capable of generating mid-IR light with very broad instantaneous bandwidth.

Selectively transporting small chiral particles with circularly polarized Airy beams

Wanli Lu, Huajin Chen, Sandong Guo, Shiyang Liu, and Lin Zhifang

Doc ID: 325209 Received 02 Mar 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: Based on the full wave simulation, we demonstrate that a circularly polarized vector Airy beam can selectively transport small chiral particles along a curved trajectory via the chirality-tailored optical forces. The transverse optical forces can draw the chiral particles with different particle chirality towards or away from the intensity maxima of the beam, leading to the selective trapping in the transverse plane. The transversely trapped chiral particles are then accelerated along a curved trajectory of the Airy beam by the chirality-tailored longitudinal scattering force, rendering an alternative way to sort and/or transport chiral particles with specified helicity. Finally, the underlying physics of the chirality induced transverse trap and de-trap phenomena are examined by the analytical theory within the dipole approximation.

High-harmonic generation in solids driven by sub-cycle mid-infrared pulses from two-color filamentation

Hideto Shirai, Fumitoshi Kumaki, Yutaka Nomura, and Takao Fuji

Doc ID: 319557 Received 15 Jan 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: Carrier-envelope phase (CEP) controlled sub-cycle mid-infrared (MIR) pulses generated through two-color filamentation have been applied for high harmonic (HH) generation in crystalline silicon (Si) membrane. The HH spectrum reaches the ultraviolet region (<300 nm), beyond the direct band gap of Si. The shape of the HH spectrum strongly depends on the CEP. The complex CEP dependence can be explained with the interference between different orders of the harmonics. The complete waveform characterization of the sub-cycle driver pulse using frequency-resolved optical gating capable of CEP determination plays a crucial role for investigation of the sub-cycle dynamics.

Isolated attosecond pulse in the water window from many-cycle laser driven plasma mirrors without pulse engineering

Zi-Yu chen

Doc ID: 322952 Received 09 Feb 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: High-order harmonic generation from relativistic laser driven plasma mirrors is an attractive route to produce highly energetic attosecond pulses in the extreme-ultraviolet to X-ray regime. To achieve an isolated attosecond pulse (IAP) driven by many-cycle intense laser pulses, pulse engineering techniques, such as polarization modulation and wave front rotation, are usually needed. Here we show it is possible to generate IAP without pulse engineering. Through particle-in-cell simulations, it is found that plasma mirrors can be rapidly heated and deformed in a relatively long preplasma regime. Intense IAP in the high-frequency spectral region is given rise once when the mirror parameters are suitable. The results may offer a new route to generate bright IAP source for various applications such as bio-imaging and electronic dynamic studies.

Continuously tunable orbital angular momentum generation controlled by the input linear polarization

Sihan Wu, Yan Li, lipeng feng, Xinglin Zeng, Wei Li, Jifang Qiu, Yong Zuo, Xiaobin Hong, Huang Yu, Rongsheng Chen, Ian Giles, and Jian Wu

Doc ID: 323201 Received 27 Feb 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: In this paper, we theoretically and experimentally demonstrate a new method to generate tunable orbital angular momentum (OAM) by continuously changing the angle of linear polarization of the input light. We use the Fourier series of left and right hand projections to prove that the average OAM smoothly varied from l=-1 to l=1 with the angle of linear polarization of input light changing from 0 to π, which is fulfilled by electrical polarization controller (PC).

Orbital angular momentum transition of light using cylindrical vector beam

Ya Han, Lei Chen, Yange Liu, Zhi Wang, Hong Zhang, Kang Yang, and Keng Chou

Doc ID: 323421 Received 16 Feb 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: We demonstrate that using a single cylindrical vector (CV) beam in the two-mode fibers, the orbital angular momentum (OAM) of light can be switched among -1, 0, and 1. The input CV beam can be a conventional radial and azimuthal polarization distribution or a generalized CV beam, and we firstly use and verify that a rocking-long period fiber grating generates the tunable generalized CV beam. Because of using a single CV beam as the light source, this approach not only provides an increased stability compared to the conventional superposed eigenmodes method, but also builds a bridge between polarization singularities beam and phase singularities beam.

Frequency upconverted amplified spontaneous emission and lasing from inorganic perovskite under simultaneous six-photon absorption

Decheng Yang, SHENGLONG CHU, Yunfeng Wang, CHUN KIT SIU, Shusheng Pan, and Siu Yu

Doc ID: 324615 Received 21 Feb 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: Multiphoton pumped stimulated emission requires simultaneous absorption of photons for the creation of population inversion to sustain optical amplification. Recently, stimulated emission by simultaneous absorption of up to five photons has been realized. To achieve more diverse nonlinear optical applications, it is desired to have more photons involving in the upconversion process. Here, we demonstrate unambiguously frequency upconverted amplified spontaneous emission and lasing via simultaneous six-photon absorption from inorganic perovskite. Our finding allows the utilization of inorganic perovskite as the novel alternative for higher-order multiphoton fluorescent applications.

Model-free deflectometry for freeform optics measurement using iterative reconstruction technique

Logan Graves, Heejoo Choi, Zhao Chuan, Chang Jin Oh, Peng Su, Tianquan Su, and Dae Wook Kim

Doc ID: 324660 Received 26 Feb 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: We present a novel model-free iterative data processing approach which improves surface reconstruction accuracy for deflectometry tests of unknown surfaces. This new processing method iteratively reconstructs the surface leading to reduced error in the final reconstructed surface. The method was implemented in a deflectometry system and a freeform surface was tested and compared to interferometric test results. The reconstructed departure from interferometric results was reduced from 44.39 µm RMS with traditional deflectometry down to 5.20 µm RMS with the iterative technique reported here.

Electro-mechanical control of an on-chip optical beam splitter containing an embedded quantum emitter

Zofia Bishop, Andrew Foster, Ben Royall, Chris Bentham, Edmund Clarke, Maurice Skolnick, and Luke Wilson

Doc ID: 321231 Received 07 Feb 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: We demonstrate electro-mechanical control of an on-chip GaAs optical beam splitter containing a quantum dot single photon source. The beam splitter consists of two nanobeam waveguides, which form a directional coupler. The splitting ratio of the directional coupler is controlled by varying the out-of-plane separation of the two waveguides using electromechanical actuation. We reversibly tune the beam splitter between an initial state, with emission into both output arms, and a final state with photons emitted into a single output arm. The device represents a compact and scalable tuning approach for use in III-V semiconductor integrated quantum optical circuits.

Stretched graded-index multimode optical fiber as novel saturable absorber for Erbium-Doped Fiber Laser Mode Locking

Wang Zhaokun, Dongning Wang, Fan Yang, liujiang Li, chunliu zhao, Ben Xu, Shangzhong Jin, Shiying Cao, and Zhanjun Fang

Doc ID: 321410 Received 05 Feb 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: A novel mode locking method based on the nonlinear multimode interference in the stretched graded-index multimode optical fiber (GIMF) is proposed in this letter. The simple device geometry, where the light is coupled in and out of the stretched GIMF via single-mode fibers (SMFs) is demonstrated to exhibit the temporal intensity discrimination required for mode-locking. The nonlinear saturable absorber (SA) characteristics of the device are controllable by simply adjusting the strength of stretching applied. The modulation depth of the device which consists of ~ .5cm GIMF is tuned from 10.37 % to 22.27 %. Such a simple SA enables the wavelength-switchable mode-locking operation in a ring Er-doped fiber laser and ultrafast pulses with pulse width of 506 fs at 1572.5 nm and 416 fs at 1591.4 nm were generated, respectively. The versatility and simplicity of the SA device together with the possibility of scaling the pulse energy make it highly attractive in ultrafast photonics.

A Flexible and Broadly Tunable Infrared Light Source based on Shaped sub-10 fs Pulses for a Multimodal Microscopy Setup

Lukas Brückner, Niklas Müller, and Marcus Motzkus

Doc ID: 324770 Received 27 Feb 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: We present a versatile approach for mid-infrared spectroscopy through the flexible control of a Difference-Frequency-Generation (DFG) process by fs pulse shaping and spectral focusing. Based on a broadband sub-10 fs oscillator the spectral position and spectral resolution can be independently selected within the molecular fingerprint region of more than 2000 cm-1. A spectral resolution better than 20 cm-1 can be achieved which depends solely on the pulse shaper configuration. An absorption experiment on a polystyrene reference sample finally validates the concept and opens the door for an additional modality in nonlinear multimodal microscopy setups.

Adaptive spatiotemporal optical pulse front tilt using MEMS mirrors and its THz application

Kosuke Murate, Mehraveh Javan Roshtkhari, xavier ropagnol, and Francois Blanchard

Doc ID: 323279 Received 14 Feb 2018; Accepted 28 Mar 2018; Posted 28 Mar 2018  View: PDF

Abstract: We report a new method to manipulate temporally and spatially the pulse front tilt (PFT) intensity profile of an ultrashort optical pulse using a commercial microelectromechanical system (MEMS), also known as a digital micromirror device (DMD). For our demonstration, we show terahertz (THz) generation in a lithium niobate crystal using the PFT pumping scheme derived from a DMD chip. The adaptive functionality of the DMD could be a convenient alternative to the more conventional grating required to generate a laser beam with a PFT intensity profile that is typically used for efficient optical rectification in noncollinear phase matching condition. In comparison with a grating, PFT using DMD does not suffer from wavelength dispersion and exhibits overlap properties between grating and a stair-step echelon mirror.

Terahertz Super-Resolution Imaging Using Four WaveMixing in Graphene

Jiang-Yu Liu, Tie-Jun Huang, and Pu-Kun Liu

Doc ID: 323021 Received 12 Feb 2018; Accepted 27 Mar 2018; Posted 28 Mar 2018  View: PDF

Abstract: A perfect lens made from negative refraction materials is utilized to overcome the diffraction limit. However, traditional perfect lenses are realized by metamaterials, which suffer from high losses and are generally bulky. In this work, we propose a terahertz negative refraction lens using four wave mixing process in graphene. Negative refraction is demonstrated because of the partial phase matching along graphene's surface. Evanescent waves that store high spatial frequency information can be converted into propagating waves in the nonlinear negative refraction process. An image with subwavelength resolution is reconstructed at the four wave mixing wavelength. Theoretical analysis and numerical simulations are performed to demonstrate the capability of such imaging. The lens has a subwavelength resolution of around λ/5. The lens needs low field intensity due to strong nonlinear response of graphene in the terahertz frequency. The work may find potential applications in terahertz microscopy.

Optical-resonance-enhanced nonlinearities in aMoS₂-coated single-mode fiber

Haojie Zhang, Noel Healy, Antoine Runge, Chung Che Huang, Daniel William Hewak, and Anna Peacock

Doc ID: 321040 Received 01 Feb 2018; Accepted 27 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: Few-layer molybdenum disulfide (MoS₂) has an electronicband structure that is dependent on the numberof layers and is, therefore, a very promising material foran array of optoelectronic, photonic and lasing applications.In this work, we make use of a side-polished opticalfiber platform to gain access to the nonlinear opticalproperties of the MoS₂ material. We show that the nonlinearresponse can be significantly enhanced via resonantcoupling to the thin film material, allowing for theobservation of optical modulation and spectral broadeningin the telecoms band. This route to access thenonlinear properties of 2D materials promises to yieldnew insights into their photonic properties.

Narrow-band double filtering hyperspectral imaging based on a single AOTF

Chunguang Zhang, hao wang, zhonghua zhang, jiangwei yuan, lei shi, zhenfei sheng, and xiaofa zhang

Doc ID: 325075 Received 28 Feb 2018; Accepted 27 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: For an acousto-optic tunable filter (AOTF), a method of spectral resolution improvement was presented based on the double-filtering in a single AOTF. A special narrow-band hyperspectral imaging system using this single-AOTF double-filtering method was established. The spectral bandwidth of double-filtered spectra was 39 % narrower than that of the single-filtered optical signal experimentally. We also got the hyperspectral images of the resolution target with better image resolution than the single-filtering images, because of the improved spectral resolution after the double-filtering process.

Coherent injection of light into absorbing scattering medium with a microscopic pore

Alexey Yamilov, Raktim Sarma, Vladislav Yakovlev, and Hui Cao

Doc ID: 320959 Received 31 Jan 2018; Accepted 27 Mar 2018; Posted 05 Apr 2018  View: PDF

Abstract: We demonstrate that an interplay between absorption and scattering in a dielectric medium with a microscopic pore gives rise to eigenchannels concentrated in the pore. Such circumvention of attenuation leads to high transmission. By exciting such eigenchannels in a disordered nano-photonic system with wave-front shaping technique, we experimentally confirm enhanced injection at depths exceeding the limiting length scales set by scattering, absorption and diffraction.

Perceptually uniform color space for visualizing trivariate linear polarization imaging data

Andrew Kruse, Andrey Alenin, Israel Vaughn, and J. Scott Tyo

Doc ID: 322557 Received 05 Feb 2018; Accepted 26 Mar 2018; Posted 06 Apr 2018  View: PDF

Abstract: The visualization of polarimetric data is often done bycolormapping the linear parameters using the three channelsin the HSV color space. Because this color spaceis not an accurate model of human color perception, theresulting visualization mixes the perceptual channels andcontains non-uniformity. We present a new mapping strategythat reliably and accurately depicts reality by placingthe polarization parameters directly into the perceptuallyuniform channels of CAM02-UCS. This mapping also ensuresthat regions of high polarization will be more visible,even when the measured irradiance is low.

2.6mJ/100Hz CEP stable near-single-cycle 4μm laser based on OPCPA and hollow-core-fiber compression

Pengfei Wang, Yanyan Li, Wenkai Li, hongpeng su, Beijie Shao, Shuai Li, Cheng Wang, Ding Wang, ruirui zhao, Yujie Peng, Yuxin Leng, Ruxin Li, and Zhizhan Xu

Doc ID: 320896 Received 30 Jan 2018; Accepted 26 Mar 2018; Posted 05 Apr 2018  View: PDF

Abstract: A carrier envelope phase stable near-single-cycle mid-infrared laser based on optical parametric chirped pulse amplification and hollow-core-fiber compression is demonstrated. 4 μm laser pulse with 11.8 mJ energy is delivered from a KTA based OPCPA with 100 Hz repetition rate, and compressed to 105 fs by a two-grating compressor with efficiency over 50%. Subsequently, the pulse spectrum is broadened by employing a krypton gas-filled hollow-core-fiber. Then, the pulse duration is further compressed to 21.5 fs through a CaF2 bulk material with energy of 2.6 mJ and stability of 0.9% RMS, which is about 1.6 cycle for 4 μm laser pulse. The carrier envelope phase of the near-single-cycle 4 μm laser pulse is passively stabilized with 370 mrad.

Practical gigahertz quantum key distribution robust against channel disturbance

Shuang Wang, Wei Chen, Zhen-Qiang Yin, De-Yong He, Cong Hui, Peng-Lei Hao, Guan-Jie Fan-Yuan, Chao Wang, Li-Jun Zhang, Jie Kuang, Shu-Feng Liu, Zheng Zhou, Yong-Gang Wang, Guang-can Guo, and Zhengfu Han

Doc ID: 320766 Received 26 Jan 2018; Accepted 26 Mar 2018; Posted 28 Mar 2018  View: PDF

Abstract: Quantum key distribution (QKD) provides a attractive solution for secure communication. However, channel disturbance severely limits its application when a QKD system is developed from laboratory to field. Here, a high-speed Faraday-Sagnac-Michelson QKD system is proposed to automatically compensate channel polarization disturbance, which largely avoid the intermittency limitations of environment mutation. Over 50 km fiber channel with 30 Hz polarization scrambling, the practicability of this phase-coding QKD system is characterized with a high interference fringe visibility of $99.35\%$ over 24 hours, and a stable secure key rate of 306k bits/s over 7 days without active polarization alignment.

Reconfigurable broadband mode (de)multiplexer based on integrated thermally-induced Long-period grating and asymmetric Y-junction

Weike Zhao, Jing feng, Kaixin Chen, and Kin Chiang

Doc ID: 324681 Received 22 Feb 2018; Accepted 25 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: We propose a reconfigurable broadband mode (de)multiplexer based on a thermally-induced long-period grating integrated with an asymmetric Y-junction. Any of the two spatial modes of a two-mode waveguide launched into the grating end of the device can be switched into any of the two output ports of the Y-junction by controlling the electric power applied to the electrode heater that induces the grating. Our typical device fabricated with polymer material, which has a length of ~14 mm, shows a mode selectivity higher than 12 dB over the C+L band at a switching power of 198 mW. The device could find applications in reconfigurable mode-division-multiplexing systems.

Coherent virtual absorption for discretized light

Stefano Longhi

Doc ID: 325083 Received 28 Feb 2018; Accepted 25 Mar 2018; Posted 28 Mar 2018  View: PDF

Abstract: Coherent virtual absorption (CVA) is a recently-introduced phenomenon for which exponentially growing waves incident onto a conservative optical medium are neither reflected nor transmitted, at least transiently. CVA has been associated to complex zeros of the scattering matrix and can be regarded as the time reversal of the decay process of a quasi-mode sustained by the optical medium. Here we consider CVA for discretized light transport in coupled resonator optical waveguides or waveguide arrays and show that a distinct kind of CVA, which is not related to complex zero excitation of quasi-modes, can be observed. This result suggests that scattering matrix analysis can not fully capture CVA phenomena.

Robust soliton crystals in a thermally controlled microresonator

Weiqiang Wang, zhizhou lu, Wenfu Zhang, Sai Tak Chu, Brent Little, Leiran Wang, Xiaoping Xie, mulong liu, Qinghua Yang, Lei wang, jianguo zhao, Guoxi Wang, Qibing Sun, Yuanshan Liu, Yishan Wang, and Wei Zhao

Doc ID: 324949 Received 01 Mar 2018; Accepted 24 Mar 2018; Posted 28 Mar 2018  View: PDF

Abstract: We demonstrate robust soliton crystals generation with a fixed frequency pump laser through thermoelectric cooler based thermal-tuning approach in a butterfly packaged CMOS-compatible microresonator. Variety of soliton crystal states, exhibiting “palm-like” optical spectra that result from the strong interactions between the dense soliton ensembles and reflect their temporal distribution directly, are experimentally observed by sweeping one cavity resonance across the pump frequency from blue-detuning side by reducing the operating temperature of the resonator. Benefitting from the tiny intra-cavity energy change, repeatable interconversion between the chaotic MI and stable soliton crystal states can be successfully achieved via simply tuning the temperature or pump power, which shows the easy accessibility and excellent stability of such soliton crystals. Our work could facilitate microresonator based optical frequency combs towards a portable, adjustable and low-cost system avoiding the requirement of delicate frequency-sweeping pump technique.

Nonlinear pulse compression in a gas filled multipass cell

Moritz Ueffing, Simon Reiger, Martin Kaumanns, Vladimir Pervak, Michael Trubetskov, Thomas Nubbemeyer, and Ferenc Krausz

Doc ID: 322807 Received 08 Feb 2018; Accepted 24 Mar 2018; Posted 28 Mar 2018  View: PDF

Abstract: We present an efficient method for compressing sub-picosecond pulses at 200 W average power with 2 mJ pulse energy in a multipass cell filled with different gases. We demonstrate spectral broadening by more than a factor of five using neon, argon and nitrogen as nonlinear media. The 210 fs input pulses are compressed down to 37 fs and 35 GW peak power with a beam quality factor of 1.3x1.5 at a power throughput of >93%. This concept represents an excellent alternative to hollow-core fiber based compression schemes and OPAs.

Fabrication of controllably variable sub-100 nm gaps in silver nanowires by photothermal-induced stress

Pintu Ghosh, JINSHENG LU, Hao Luo, Ziquan Xu, XIAOYUAN YAN, yewu wang, Jun Lu, Min Qiu, and Qiang Li

Doc ID: 323465 Received 19 Feb 2018; Accepted 24 Mar 2018; Posted 28 Mar 2018  View: PDF

Abstract: A technique to fabricate nanogaps with controllably variable gap width in silver (Ag) nanowires (NWs) by photothermal-induced stress utilizing a focused continuous wave laser (532 nm) is presented. For the case of an Ag NW on gold thin film, a gap width starting from ~ 20 nm is achieved with a critical minimum power (CMP) of about 160 mW. Whereas in case of an Ag NW placed on top of a zinc oxide NW, the attained gap width is as small as a few nm (< 10 nm) with a CMP of only ~ 100 mW. In both cases, the CMP is much lower as compared to the required CMP (~ 280 mW) for an Ag NW placed on a bare silica substrate. The photothermal-induced stress combined with melting/sublimation of silver aids in breaking the Ag NW. In particular, the former one plays a key role in attaining extremely narrow gap. This technique to fabricate sub-100 nm nanogaps in metal NWs can be extensively implemented in fabrication and maintenance of nanomechanical, nanoplasmonic, and nanoelectronic devices.

Sparse-fast-Fourier-transform-based quick synchronization for optical direct detection orthogonal frequency division multiplexing systems

Qiong Wu, Yating Xiang, Yizhao Chen, Ming Tang, Songnian Fu, and Deming Liu

Doc ID: 323395 Received 15 Feb 2018; Accepted 24 Mar 2018; Posted 27 Mar 2018  View: PDF

Abstract: OFDM has always been a promising candidate for optical access networks. However, it is very sensitive to synchronization errors and requires complex DSP to eliminate this influence, thus increasing the computation complexity, delay and system cost, which hampers its applications in cost-sensitive and low-latency scenarios of future optical access networks. To deal with this issue, a sparse-FFT based quick synchronization algorithm for optical direct detection (ODD)-OFDM systems is proposed and demonstrated with greatly reduced computation complexity. Detailed simulations and experimental verifications along 50 km standard single mode fiber (SSMF) transmission prove the efficiency, accuracy and feasibility of the sparse-FFT based synchronization technique in cost and delay sensitive applications for next generation optical access networks.

Selection of target elements for laser-produced plasma soft x-ray sources

Toshiki Tamura, Goki Arai, Yoshiki Kondo, Hiroyuki Hara, Tadashi Hatano, Takeo Ejima, Weihua Jiang, Chihiro Suzuki, Gerard O'Sullivan, and Takeshi Higashiguchi

Doc ID: 320545 Received 31 Jan 2018; Accepted 24 Mar 2018; Posted 28 Mar 2018  View: PDF

Abstract: We demonstrated the upper limitation to the number of shots, i.e., target lifetime, together with the number of photons emitted in the water-window soft x-ray spectral region from a number of targets used as sources in this spectral region, for multi-shot irradiation at the same position on the target surface. The spectra involved result from unresolved transition arrays (UTA) originating from n = 3 − n = 4 transitions in medium-Z element plasmas and from n = 4 − n = 4 transitions originating in high-Z plasmas. The output flux was maintained for the highest number of shots in the case of the high melting point element molybdenum (Mo) and the total output in the water window was 7.7 × 10¹³ photons/sr at a laser power density of 2.2 × 10¹⁴ W/cm².

Residue number system arithmetic based on integrated nanophotonics

Jiaxin Peng, SHUAI SUN, Vikram Narayana, Volker Sorger, and Tarek El-Ghazawi

Doc ID: 319723 Received 29 Jan 2018; Accepted 24 Mar 2018; Posted 26 Mar 2018  View: PDF

Abstract: Residue number system (RNS) enables dimensionality reduction of an arithmetic problem by representing a large number as a set of smaller integers, where the number is decomposed by prime number factorization. These reduced problem sets can then be processed independently and in parallel, thus improving computational efficiency and speed. Here we show an optical RNS hardware representation based on integrated nanophotonics. The digit-wise shifting in RNS arithmetic is expressed as spatial routing of an optical signal in 2×2 hybrid photonic-plasmonic switches. Here the residue is represented by spatially shifting the input waveguides relative to the routers' outputs, where the moduli are represented by the number of waveguides. By cascading the photonic 2×2 switches, we design a photonicRNSadderandamultiplierforminganall-to all sparse directional network. The advantage of this photonic arithmetic processor is the short (10’s ps) computational execution time given by the optical propagation delay through the integrated nanophotonic router. Furthermore, we show how photonic processing in-the-network leverages the natural parallelism of optics such as wavelength-division-multiplexing in this RNS processor. A key application for such a photonic RNS engine is the functional analysis of convolutional neural networks.

Multimodality Endoscopic Optical Coherence Tomography and Fluorescence Imaging Technology for Visualization of Layered Architecture and Subsurface Microvasculature

Yan Li, Josehp Jing, Junxiao Yu, Buyun Zhang, Tiancheng Huo, Qiang Yang, and Zhongping Chen

Doc ID: 323366 Received 19 Feb 2018; Accepted 23 Mar 2018; Posted 26 Mar 2018  View: PDF

Abstract: Endoscopic imaging technologies, such as endoscopic optical coherence tomography (OCT) and near infrared (NIR) fluorescence have been used to investigate vascular and morphological changes as hallmarks of early cancer in the gastrointestinal (GI) tract. Here, we developed a high speed multimodality endoscopic OCT and fluorescence imaging system. Using this system, the architectural morphology and vasculature of the rectum wall were obtained simultaneously from a Sprague Dawley (SD) rat in vivo. This multimodality imaging strategy in a single imaging system permits the use of a single imaging probe, thereby improving prognosis by early detection and reducing costs

Enhanced photon-phonon cross-Kerr nonlinearity with two photon driving

Tai-Shuang Yin, Xin Lu, Liang-Liang Wan, Shang-Wu Bin, and Ying Wu

Doc ID: 322700 Received 07 Feb 2018; Accepted 23 Mar 2018; Posted 28 Mar 2018  View: PDF

Abstract: We propose a scheme to significantly enhance the cross-Kerr nonlinearity between photons and phonons in a quadratically coupled optomechanical system (OMS) with two photon driving. This cross-Kerr nonlinear enhancement originates from the parametric-drivinginduced squeezing and the underlying nonlinear optomechanical interaction. Moreover, the noise of the squeezed mode can be suppressed completely by introducing a squeezed vacuum reservoir. As a result of this dramatic nonlinear enhancement and the suppressed noise, we demonstrate the feasibility of the quantum nondemolition measurement of the phonon number in an originally weak coupled OMS. In addition, the photon-phonon blockade phenomenon is also investigated in this regime, which allows for performing manipulations between photons and phonons. Our work offers a promising route towards the potential application for the OMS in quantum information processing and quantum networks.

Fast hyperspectral phase and amplitude imaging in scattering tissue

Cong Ba, Jean-Marc Tsang Min Ching, and Jerome Mertz

Doc ID: 324908 Received 27 Feb 2018; Accepted 22 Mar 2018; Posted 26 Mar 2018  View: PDF

Abstract: Hyperspectral imaging in scattering tissue generally suffers from low light collection efficiency. In this letter we propose a microscope based on Fourier transform spectroscopy and oblique back-illumination microscopy that provides hyperspectral phase and amplitude images of thick, scattering samples with high throughput. Images can be acquired at >0.1Hz rates with spectral resolution better than 200cm-1 over a wide spectral range of 450-1700nm. Proof of principle demonstrations are presented with chorioallantoic membrane (CAM) of a chick embryo, illustrating the possibility of high resolution hemodynamics imaging in thick tissue, based on transmission contrast.

Using Temperature to Reduce Noise in Quantum Frequency Conversion

Paulina Kuo, Jason Pelc, Carsten Langrock, and Martin Fejer

Doc ID: 320258 Received 14 Feb 2018; Accepted 22 Mar 2018; Posted 27 Mar 2018  View: PDF

Abstract: Quantum frequency conversion (QFC) is important in quantum networks to interface nodes operating at different wavelengths and to enable long-distance quantum communication using telecommunications wavelengths. Unfortunately, frequency conversion in actual devices is not a noise-free process. One main source of noise is spontaneous Raman scattering, which can be reduced by lowering the device operating temperature. We explore frequency conversion of 1554 nm photons to 837 nm using a 1813 nm pump in a periodically poled lithium niobate waveguide device. By reducing the temperature from 85 °C to 40 °C, we show dark count rates can be reduced significantly, which is in good agreement with theory.

Photon Pair Generation with Tailored Frequency Correlations in Graded-Index Multimode Optical Fibers

Arash Mafi and Hamed Pourbeyram

Doc ID: 324595 Received 21 Feb 2018; Accepted 22 Mar 2018; Posted 23 Mar 2018  View: PDF

Abstract: We study theoretically the generation of photon pairs with controlled spectral correlations via the four-wave mixing (FWM) process in graded-index multimode optical fibers (GIMFs). We show that the quantum correlations of the generated photons in GIMFs can be preserved over a wide spectral range for a tunable pump source. Therefore, GIMFs can be utilized as quantum-state-preserving tunable sources of photons. In particular, we have shown that it is possible to generate factorable two-photon states, which allow for heralding of pure-state single-photons without the need for narrow-band spectral post filtering. We also elaborate on the possibility of simultaneously generating correlated and uncorrelated photon pairs in the same optical fiber.

Ultrafast time-stretch microscopy based on dual-comb asynchronous optical sampling

Xin Dong, Xi Zhou, Jiqiang Kang, Liao Chen, Zihui Lei, Chi Zhang, Kenneth Kin-Yip Wong, and Xinliang Zhang

Doc ID: 324791 Received 23 Feb 2018; Accepted 22 Mar 2018; Posted 28 Mar 2018  View: PDF

Abstract: The ultrafast time-stretch microscopy based on single-pixel detector has become hotspot of the research, owing to its high sensitivity compared with those pixel sensors. However, GHz or tens of GHz acquisition bandwidth is required for this scheme, which results in great expense for the whole imaging system, and hinders its wide applications. In this paper, a dual-comb asynchronous optical sampling (ASOPS) is applied for the conventional time-stretch microscopy, whose ultrafast temporal axis is magnified by 9200 times. The acquisition bandwidth requirement is thus greatly relaxed, and 320-kHz bandwidth successfully resolves 2.3-μm spatial resolution with tens of kilohertz frame rate.

Time Domain Diffuse Raman spectrometer based on novel TCSPC camera for depth analysis of diffusive media

Sanathana Konugolu Venkata Sekar, sara mosca, Sebastian Tannert, Gianluca Valentini, Fabrizio Martelli, Tiziano Binzoni, Yury Prokazov, Evgeny Turbin, werner zuschratter, Rainer Erdmann, and Antonio Pifferi

Doc ID: 322540 Received 16 Feb 2018; Accepted 22 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: We present a time domain diffuse Raman spectrometer for depth probing of highly scattering media. The system is based on a novel TCSPC camera that simultaneously acquires both spectra and temporal information of Raman photons. A dedicated non-contact probe was built, and time domain Raman measurements were performed on a tissue mimicking bilayer phantom. The fluorescence contamination of Raman signal was eliminated by early time gating (0-212 ps) the Raman photons. Depth sensitivity is achieved by time gating Raman photons at different delays with a gate width of 106 ps. Importantly, time domain can completely decouple the Raman signal of the two layers as early gates contain only the top layer signal. As a result, an enhancement factor of 2170 was found for our bilayer phantom which is much higher than the values obtained by spatial offset Raman spectroscopy (SORS), frequency offset Raman spectroscopy (FORS) or hybrid FORS-SORS on a similar phantom.

Efficient point-by-point Bragg gratings fabricated in embedded laser-written silica waveguides using ultrafast Bessel beams

Guodong Zhang, Cheng Guanghua, Manoj Bhuyan, ciro d'amico, and Razvan Stoian

Doc ID: 321129 Received 31 Jan 2018; Accepted 21 Mar 2018; Posted 03 Apr 2018  View: PDF

Abstract: We demonstrate highly efficient Bragg gratings written point-by-point by sequential single pulse ultrashort Bessel laser beams in laser photoinscribed single mode waveguides in bulk fused silica. The use of chirped non-diffractive Bessel beams determines a strong Bragg resonance in a weak-to-strong transitional regime, augmenting to a record value of 40\,dB/cm at 1550\,nm in the third order. The Bessel-induced refractive index modulation is negative and localized to sub-micron (200\,nm) transverse scales. The strong light confinement in Bessel beams ensuring uniform one-dimensional void conditions allows thus for enhanced precision in the Bragg grating waveguide design. We demonstrate flexible fabrication of multiplexed waveguide gratings for multiple and tunable spectral resonances.

Distributed fiber sparse-wideband vibration sensing by sub-Nyquist additive random sampling

Jingdong Zhang, Hua Zheng, Tao Zhu, Guolu Yin, Min Liu, Yongzhong Bai, Dingrong Qu, FENG QIU, and Xianbin Huang

Doc ID: 325036 Received 02 Mar 2018; Accepted 20 Mar 2018; Posted 21 Mar 2018  View: PDF

Abstract: The round trip time of the light pulse limits the maximum detectable vibration frequency response range of phase-sensitive optical time domain reflectometry (φ-OTDR). Unlike the uniform laser pulse interval in conventional φ-OTDR, we randomly modulate the pulse interval, so that an equivalent sub-Nyquist additive random sampling (sNARS) is realized for every sensing point of the long interrogation fiber. For an φ-OTDR system with 10 km sensing length, the sNARS method is optimized by theoretical analysis and Monte Carlo simulation, and the experimental results verify that a wide-band spars signal can be identified and reconstructed. Such a method can broaden the vibration frequency response range of φ-OTDR, which is of great significance in sparse-wideband-frequency vibration signal detection, such as rail track monitoring and metal defect detection.

Towards femtosecond-level intrinsic Laser Synchronization at 4th Generation Lightsources

Min Chen, Sergey Kovalev, Nilesh Awari, Zhe Wang, Semyon Germanskiy, Bert Green, Jan Deinert, and Michael Gensch

Doc ID: 324753 Received 09 Mar 2018; Accepted 20 Mar 2018; Posted 26 Mar 2018  View: PDF

Abstract: In this letter, the proof of principle for a scheme providing intrinsic femtosecond-level synchronization between an external laser system and 4th generation light sources is presented. The scheme is applicable at any accelerator-based light source that is based on the generation of coherent radiation from ultra-short electron bunches such as superradiant terahertz (THz) facilities or X-FEL’s. It makes use of a superradiant THz pulse generated by the accelerator as an intrinsically synchronized gate signal for electro-optical slicing. We demonstrate that the scheme enables a reduction of the timing instability by more than two orders of magnitude. This demonstration experiment thereby proves that intrinsically synchronized time-resolved experiments utilizing laser and accelerator-based radiation pulses on few tens of femtosecond (fs) to few fs timescales are feasible.

Propagation and refraction of left-handed plasmons on a semiconducting substrate covered by graphene

Amirparsa Zivari, Amirmasood Bagheri, Behzad Rejaei, and Amin Khavasi

Doc ID: 324581 Received 21 Feb 2018; Accepted 19 Mar 2018; Posted 23 Mar 2018  View: PDF

Abstract: We show that a graphene layer mounted on a plasmonic semiconductor substrate can support highly confined surface plasmon polaritons with left-handed characteristics. This occurs when the imaginary part of graphene conductivity and real part of the effective permittivity of the surrounding medium become simultaneously negative. Full wave electromagnetic simulations demonstrate the occurrence of negative refraction and 2D lensing at the interface separating regions supporting conventional right-handed graphene plasmons and left-handed surface plasmon polaritons.

Nanobomb optical coherence elastography

Kirill Larin, Chih Hao Liu, Dmitry Nevozhay, Alexander Schill, Manmohan Singh, Susobhan Das, Achuth Nair, Zhaolong Han, Salavat Aglyamov, and Konstantin Sokolov

Doc ID: 323033 Received 16 Feb 2018; Accepted 17 Mar 2018; Posted 21 Mar 2018  View: PDF

Abstract: Wave-based optical elastography is rapidly emerging as a powerful technique for quantifying tissue biomechanical properties due to its noninvasive nature and high displacement sensitivity. However, current optical elastography approaches are limited in their ability to produce high frequency waves and highly localized mechanical stress. In this work, we demonstrate that the rapid liquid-to-gas phase transition of dye-loaded perfluorocarbon (PFC) nanodroplets ("nanobombs") initiated by a pulsed laser can produce highly localized, high frequency, and broadband elastic waves. The waves were detected by an ultra-fast line-field low-coherence holography system. For comparison, we also excited waves using focused micro air-pulse. Measurements in tissue-mimicking phantoms showed that the nanobombs produced elastic waves with frequencies up to ~9 kHz, which was much greater than the ~2 kHz waves excited by the air-pulse. Consequently, the nanobombs enabled more accurate quantification of sample viscoelasticity. Combined with their potential for functionalization, the nanobombs show promise for accurate and highly specific noncontact all-optical elastography.

Single-exposure full-field multi-depth imaging using low-coherence holographic multiplexing

Lauren Wolbromsky, Nir Turko, and Natan Shaked

Doc ID: 322520 Received 06 Feb 2018; Accepted 13 Mar 2018; Posted 21 Mar 2018  View: PDF

Abstract: We present a new interferometric imaging approach, which allows for multiple-depth imaging in a single acquisition, using off-axis low-coherence holographic multiplexing. This technique enables sectioned imaging of multiple slices within a thick sample, in a single image acquisition. Each slice has a distinct off-axis interference fringe orientation indicative of its axial location, and the camera acquires the multiplexed hologram containing the different slices at once. We demonstrate the proposed technique for amplitude and phase imaging of optically thick samples.

Gas spectroscopy with integrated frequency monitoring through self-mixing in a terahertz quantum-cascade laser

Rabi Chhantyal-Pun, Alex Valavanis, James Keeley, Pierluigi Rubino, Iman Kundu, Yingjun Han, Paul Dean, Lian He Li, Giles Davies, and Edmund Linfield

Doc ID: 323151 Received 15 Feb 2018; Accepted 12 Mar 2018; Posted 15 Mar 2018  View: PDF

Abstract: We demonstrate a gas spectroscopy technique, using self-mixing in a 3.4-THz quantum-cascade laser (QCL). All previous QCL spectroscopy techniques have required additional THz instrumentation (detectors, mixers or spectrometers) for system pre-calibration or spectral analysis. By contrast, our system self-calibrates the laser frequency (i.e., with no external instrumentation) to a precision of 630 MHz (0.02%) by analyzing QCL voltage perturbations in response to optical feedback within a 0-800-mm round-trip delay-line. We demonstrate methanol spectroscopy by introducing a gas cell into the feedback path, and show that a limiting absorption coefficient of ~1e-4 / cm is resolvable.

A Flexible Approach to Vibrational Sum Frequency Generation using Shaped Near Infrared Light


Doc ID: 321144 Received 02 Feb 2018; Accepted 03 Mar 2018; Posted 23 Mar 2018  View: PDF

Abstract: We describe a new approach that expands the utility of vibrational sum-frequency generation (vSFG) spectroscopy using shaped near infrared (NIR) laser pulses. We demonstrate that arbitrary pulse shapes can be specified to match experimental requirements without the need for change to the optical alignment. In this way, narrowband NIR pulses as long as 5.75 ps are readily generated, with a spectral resolution of about 2.5 cm-1, an improvement of approximately a factor of 3 compared to a typical vSFG system. Moreover, the utility of having complete control over the NIR pulse characteristics is demonstrated through non-resonant background suppression from a metallic substrate by generating an etalon waveform in the pulse shaper. The flexibility afforded by switching between arbitrary NIR waveforms, at the sample position with the same instrument geometry, expands the type of samples that can be studied without extensive modifications to existing apparatus or large investments in specialty optics.

Filamentation of Mid-IR pulses in ambient air in the vicinity of molecular resonances

Valentina Shumakova, Skirmantas Alisauskas, Pavel Malevich, Claudia Gollner, Andrius Baltuska, Daniil Kartashov, Aleksei Zheltikov, Alexander Mitrofanov, Aleksandr Voronin, Dmitry Sidorov-Biryukov, and Audrius Pugzlys

Doc ID: 322812 Received 08 Feb 2018; Accepted 26 Feb 2018; Posted 05 Mar 2018  View: PDF

Abstract: Properties of filaments ignited by multi-millijoule, 90 fs mid-IR pulses centered at 3.9 µm are examined experimentally by monitoring plasma density and losses as well as spectral dynamics and beam profile evolution at different focusing strengths. By softening the focusing from strong (f=0.25 m) to loose (f=7 m) we observe a shift from plasma assisted filamentation to filaments with low plasma density. In the latter case, filamentation manifests itself by beam self-symmetrization and spatial self-channeling. Spectral dynamics in the case of loose focusing is dominated by the non-linear Raman frequency downshift, which leads to the overlap with the CO2 resonance in the vicinity of 4.2 µm. The dynamic CO2 absorption in the case of 3.9 µm filaments with their low plasma content is the main mechanism of energy losses and either alone or together with other nonlinear processes contributes to the arrest of intensity.

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