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Mach-Zehnder interferometer with quantum beamsplitters

Daniel Valente, Nelson Almeida, and Thiago Werlang

Doc ID: 368133 Received 21 May 2019; Accepted 11 Oct 2019; Posted 11 Oct 2019  View: PDF

Abstract: The quantum beamsplitter -- a two-level system (TLS) coupled to a one-dimensional continuum of electromagnetic modes -- is the most elementary version of a beamsplitter which may not only refract and reflect, but also absorb then reemit a photon. This raises the question of whether a single-photon pulse, once split by a first quantum beamsplitter, could be made to interfere by a second one. Here, we propose and theoretically analyze a quantum Mach-Zehnder interferometer (QMZ) as formed by two concatenated quantum beamsplitters. The distinctive feature of our QMZ is its appreciable saturability for a single photon, arising from the broadband nature of the pulse. We show that (i) off-resonant monochromatic photons produce classical interference patterns, whereas (ii) resonant broadband pulses erase these patterns, and that (iii) off-resonant broadband pulses always preserve some degree of interference if the two TLSs are oppositely detuned.

Dynamically tunable and transmissive linear to circular polarizer based on graphene metasurface

zhifei yao, mengjia lu, Chunyang Zhang, and yueke wang

Doc ID: 373935 Received 29 Jul 2019; Accepted 10 Oct 2019; Posted 11 Oct 2019  View: PDF

Abstract: A dynamically tunable and transmissive polarization converter, based on graphene metasurface, has been proposed in terahertz range. In this paper, the left-handed circular polarization(LHCP) with bandwidth from 5.15 to 5.52 THz is realized due to the superimposition of the two transmissive orthogonal components with a near 90°phase difference. By varying the fermi energy, the working frequencies of the converter can be dynamically controlled, which also imply the linear to circular polarization conversion originates from the excitation of graphene surface plasmon. Besides, the absorption loss decreases with increasing electron scattering time. All simulation results have been conducted by finite element method(FEM).

Phase-dependent light-induced torque

S. Hamide Kazemi and Mohammad Mahmoudi

Doc ID: 374351 Received 31 Jul 2019; Accepted 10 Oct 2019; Posted 11 Oct 2019  View: PDF

Abstract: We study an optical torque, emerging through the interaction of orbital angular momentum with atoms/molecules, in quantum systems with closed-loop interactions. First, we show how atoms with a closed-loop scheme experience a well-controlled torque whose features depend on the relative phase of applied fields. Such controllable torque, along with simplicity of tuning the relative phase, can simplify the implementation of current flows in atomic Bose-Einstein condensates. Moreover, we calculate the optical torque exerted on chiral molecules with cyclic-transition structures, and find that the enantiomers can experience different torques, for proper choice of the parameters. Such feature may find applications in sorting and separation of enantiomers.

Ultrabroadband infrared near-field spectroscopy and imaging of local resonators in percolative gold films

Xinzhong Chen, Jiawei Zhang, Ziheng Yao, Hans Bechtel, Michael Martin, Larry Carr, and Mengkun Liu

Doc ID: 375467 Received 15 Aug 2019; Accepted 10 Oct 2019; Posted 11 Oct 2019  View: PDF

Abstract: Percolation processes are ubiquitous in nature and are responsible for many critical phenomena, such as first-order phase transitions and infectious epidemic networks. The optical properties of a percolative medium can generally be captured by the effective medium approximation (EMA) when the degree of percolation and the properties of the constituent materials are properly addressed. However, the important local collective responses of nanoclusters in the deep subwavelength regime are often only phenomenologically addressed in the standard EMA formalism. A comprehensive method that measures local light-matter interactions and registers how the local responses influence global optical properties has yet to be established on a firm basis. In this letter, we use infrared nano-imaging/ spectroscopy to investigate percolative gold films at the vicinity of the critical percolation threshold. We demonstrate experimentally and theoretically that the near-field spectra yield quantitative information of the characteristic length scale of the local gold clusters and their relative oscillator strengths. As a result, EMA analysis can be augmented with nano-spectroscopy to yield better predictability of the infrared spectrum at the corresponding spectral range.

Randomized Spectral Sampling for Efficient Simulation of Laser Propagation through Optical Turbulence

Daniel Paulson, Chensheng Wu, and Christopher Davis

Doc ID: 364627 Received 09 Apr 2019; Accepted 10 Oct 2019; Posted 11 Oct 2019  View: PDF

Abstract: We present a new method for the generation of atmospheric turbulence phase screens based on the frequency shift property of the Fourier transform. This method produces low spatial frequency distortions without additional computation time penalties associated with methods using subharmonic subgrids. It is demonstrated that for simulations of atmospheric turbulence with finite outer scales, the performance of our method with respect to the statistical phase structure of the screen meets or exceeds other methods with respect to agreement with theory. We outline small-scale accuracy issues associated with modelling non-Kolmogorov spectral power laws using existing techniques, and propose a solution. For simulations of long-range propagation through atmospheric optical turbulence, our method provides various advantages over standard methods.

Preserving nonclassical correlations in strongly unbalanced conditions

Alessia Allevi and Maria Bondani

Doc ID: 371259 Received 28 Jun 2019; Accepted 09 Oct 2019; Posted 09 Oct 2019  View: PDF

Abstract: It is well known that optical losses represent the main obstacle to the real exploitation of quantum optical systems for quantum technology. Here we investigate to which extent the presence of unbalanced losses between the two parties of a mesoscopic twin-beam state can prevent or not the observation of nonclassical correlations. Moreover, we focus on the survival of nonclassicality in the presence of asymmetric lossy channels modelled according to specific statistical distributions.

Optical Precursors in a Weakly Dispersive Double Narrow Resonance Dielectric

Heejeong Jeong, Chang-Won Lee, Andrew Dawes, and Daniel Gauthier

Doc ID: 373900 Received 29 Jul 2019; Accepted 08 Oct 2019; Posted 08 Oct 2019  View: PDF

Abstract: We investigate optical precursors transmitted through a double Lorentz dielectric consisting of two adjacent narrow resonances. The transmitted envelop shows additional modulation patterns compared to the patterns in a single Lorentz dielectric that oscillates at the separation frequency between two resonances corresponding to the doublet frequency separation. We use the weakly-dispersive, narrow-resonance (WDNR) condition to analyze it, which compares favorably to our observations. This work will be meaningful to identify dielectric properties by analyzing the multi-resonant media for application of optical communication.

Potential of Bessel spiral zone plate in complex beam shaping and structuring

Arash Sabatyan and Seyyed Mojtaba Taheri

Doc ID: 376259 Received 26 Aug 2019; Accepted 08 Oct 2019; Posted 08 Oct 2019  View: PDF

Abstract: We aim here to show that azimuthal structuring of the optical beam may be realized by apodizing spiral zone plate using an azimuthal modulated Bessel function. We demonstrate that the azimuthal modulation of a Bessel beam may cause its transmittance to take negative values in azimuth. Accordingly, when a diffractive element (herein spiral zone plate) is apodized by such a modulated Bessel function its transmittance undergoes an azimuthally phase change which imposes that phase change on a beam passing through it. This means that the technique enables us to produce a variety of azimuthal beam shapes like a spiral, ring-lattice, light-arm, and multi-spot beams. In this research, we illustrate how these structures and shapes are produced and tailored. To verify the consequences of the simulation, the corresponding experiments were planned.

Wavelength scaling laws for high-order harmonic yield from atoms driven by mid- and long-wave infrared laser fields

Mikhail Emelin, Mikhail Ryabikin, and Anna Emelina

Doc ID: 376522 Received 28 Aug 2019; Accepted 07 Oct 2019; Posted 08 Oct 2019  View: PDF

Abstract: High-order harmonic generation (HHG) in gases is known to benefit from using midinfrared driving laser fields, since, due to a favorable wavelength scaling of the electron ponderomotive energy, higher-energy photon production becomes feasible with longer-wavelength drivers. On the other hand, recent studies have revealed a number of physical effects whose importance for HHG increases with increasing laser wavelength. These effects, as a rule, result not only in a general decrease of the harmonic yield but also in a reshaping of the emission spectrum. Therefore, the detailed study of the dependence of HHG yield on the laser wavelength has become important issue for producing intense extremely short XUV and x-ray pulses using HHG driven by long-wavelength laser fields. Here, we address this issue by calculating the HHG spectra for laser wavelengths ranging from 2 to 20 µm. This study has been carried out in frame of strong-field approximation modified properly to take into account the atomic bound-state depletion and the effect of the magnetic field of a laser pulse on the dynamics of the field-ionized electron. We show that different regions of the HHG spectrum behave differently with the laser wavelength and discuss the origins of this behavior. The analytical formulas are derived that match well the calculated wavelength scalings.

Nonlinear propagation characteristics of a radially polarized beam in a uniaxially aligned dye-doped liquid crystal

Moritsugu Sakamoto, Naoto Matsuo, Kohei Noda, Tomoyuki Sasaki, Nobuhiro Kawatsuki, and Hiroshi Ono

Doc ID: 368916 Received 04 Jun 2019; Accepted 07 Oct 2019; Posted 08 Oct 2019  View: PDF

Abstract: The nonlinear propagation characteristics of a radially polarized (RP) beam in uniaxially aligned dye-doped liquid crystal (DDLC) were investigated in experiments and theorly. The photothermal effect produces changes in the refractive index of the nonlinear polarization-sensitive medium, in both ordinary and extraordinary directions. The changes promote a self-modulation of the polarization pattern in the incident RP beam as it propagates through the DDLC. The experiemntal results are explained from theory by modeling the change in the refractive index of the medium. Our results may be applied to spatial polarization modulation, by which an axially symmetric polarized beam is converted into another structured light such as the full Poincar\'e beam.

Modulating quantum fluctuations of scattered lights in disordered media via wavefront shaping

Dong Li and Yao Yao

Doc ID: 373613 Received 24 Jul 2019; Accepted 07 Oct 2019; Posted 08 Oct 2019  View: PDF

Abstract: After multiple scattering of quadrature-squeezed lights in a disordered medium, the quadrature amplitudes of the scattered modes present an excess noise above the shot-noise level [Opt. Expr. 14, 6919 (2006)]. A natural question is raised whether there exists a method of suppressing the quadrature fluctuation of the output mode. The answer is affirmative. In this work, we prove that wavefront shaping is a promising method to reduce the quantum noise of quadrature amplitudes of the scattered modes. This reduction is owing to the destructive interference of quantum noise. Specifically, when the single-mode squeezed states are considered as inputs, the quantum fluctuation can always be reduced, even below the shot-noise level. These results may have potential applications in quantum information processing, for instance, sub-wavelength imaging using the scattering superlens with squeezed-state sources.

Numerical study on mid-infrared optical parametric oscillation around 5 μm by injecting signal vector beams in an As2Se2 MOFs

Weiqing Gao, Peng Wang, Wenhui Jiang, Zhengxiong Zhang, Xiu Zhang, Panyun Gao, Zhang Wei, Meisong Liao, Takenobu Suzuki, Yasutake Ohishi, and Zhou Yong

Doc ID: 373885 Received 26 Jul 2019; Accepted 04 Oct 2019; Posted 08 Oct 2019  View: PDF

Abstract: The influence of the core diameter and pump wavelength on the phase-matching conditions when the different signal vector beams are injected is analyzed numerically in a suspended-core As2Se3 microstructured optical fiber (MOF). The idle wavelengths satisfying the phase-matching conditions with different signal vector beams can arrive the wavelengths 4.8-5.9 μm in the As2Se3 MOFs with different core diameters. By changing the signal vector mode field and adjusting the corresponding signal wavelength, the idler wavelength can be tuned in 754.8 nm from 4.9182 to 5.6730 μm with the pump wavelength changing from 2.80 to 2.90 μm. The influence on signal gain and the idler conversion efficiency is calculated in the As2Se3 MOFs with different lengths when injecting different signal vector beams. The signal and idle conversion efficiency can arrive ~28 dB and ~24%, respectively, when the different signal vector beams are injected. The simulated results demonstrate that the optical parametric oscillation with the wavelengths longer than 5 μm can be realized in chalcogenide fibers with the signal vector beams injecting.

Controlling spatial hole burning in lasers using anisotropic laser mirrors

Jean-Francois Bisson and Koffi Amouzou

Doc ID: 374183 Received 30 Jul 2019; Accepted 04 Oct 2019; Posted 08 Oct 2019  View: PDF

Abstract: The concept of the twisted-mode laser operation, which suppresses spatial hole burning and produces single mode operation in a standing wave resonator, is revisited for the case of optically anisotropic laser mirrors presenting arbitrary birefringent and dichroic properties. Our analysis clarifies the relationship between the mirrors’ optical properties and the proximity of the polarization states of the counter-propagating waves, which determines the visibility of the standing wave pattern inside the resonator. The intensity of the principal mode and the population of excited states as a function of the pumping rate are then determined analytically and enable estimates of the slope efficiency and threshold of multimode emission for a given value of the proximity factor. The excited state population is found to reach an upper bound as a function of the pumping rate, for every value of the proximity factor, except unity. Design rules of anisotropic mirrors for producing single frequency operation are provided that are less strict than those for achieving pure twisted mode operation.

Stable Numerical Schemes for Nonlinear Dispersive Equations with Counter-Propagation and Gain Dynamics

J. Kutz, Steven Cundiff, Herbert Winful, Mark Dong, Chang Sun, and Niall Mangan

Doc ID: 371065 Received 27 Jun 2019; Accepted 03 Oct 2019; Posted 04 Oct 2019  View: PDF

Abstract: We develop a stable and efficient numerical scheme for modeling the optical field evolution in a nonlinear dispersive cavity with counter propagating waves and complex, semiconductor physics gain dynamics that are expensive to evalute. Our stability analysis is characterized by a von-Neumann analysis which shows that many standard numerical schemes are unstable due to competing physical effects in the propagation equations. We show that the combination of a predictor-corrector scheme with an operator-splitting not only results in a stable scheme, but provides a highly efficient, single-stage evaluation of the gain dynamics. Given that the gain dynamics is the rate-limiting step of the algorithm, our method circumvents the numerical instability induced by the other cavity physics when evaluating the gain in an efficient manner. We demonstrate the stability and efficiency of the algorithm on a diode laser model which includes three waveguides and semiconductor gain dynamics. The laser is able to produce a repeating temporal waveform and stable optical comblines, thus demonstrating that frequency combs generation may be possible in chip scale, diode lasers.

Extraction of effective constitutive parameters of artificial media using Bloch modes

Behzad Rejaei and Abbas Sheikh Ansari

Doc ID: 373637 Received 24 Jul 2019; Accepted 01 Oct 2019; Posted 02 Oct 2019  View: PDF

Abstract: The effective constitutive parameters of a three-dimensional periodic structure are calculated using its Bloch modes. These modes and their propagation constants are obtained from eigenvectors and eigenvalues of the generalized transfer matrix of a unit layer of the structure. Effective, bulk permittivity and permeability tensors of the medium are obtained when two of the Bloch modes are dominant, i.e., propagate without significant decay inside the medium. The effect of the strongly decaying Bloch modes, that are excited at the interface with a conventional medium, are included by means of surface impedance matrices. The results are in excellent agreement with full-wave electromagnetic simulations.

Diffraction-ray tubes analysis of ultrashort high-intense laser pulse filamentation in air

Yuri Geints, Olga Minina, and Alexander Zemlyanov

Doc ID: 361851 Received 07 Mar 2019; Accepted 01 Oct 2019; Posted 02 Oct 2019  View: PDF

Abstract: The results of theoretical simulation of femtosecond Ti:Sapphire laser pulses propagation in air in the self-focusing and filamentation regimes are presented. The self-focusing of pulsed radiation was analyzed based on the diffraction ray tracing method, within which the beam power propagates within specific light structures, known as the diffraction-ray tubes. These tubes do not intersect in space, do not exchange their energy, but the changes in their shape and cross-section reflect the physical effects occurring with the radiation during its propagation through the medium. This allows discovering the formation of specific light structures in a laser beam during its self-focusing. One of these structures is the energy-replenishing diffraction-ray tube (ERT), which provides the filamentation domain with the necessary light energy and exists also in the form of a high-intensity light channel during the post-filamentation propagation of a pulse. The dependences of the radius and power of this energy-replenishing tube on the initial beam radius and peak radiation power at a fixed pulse length are derived. It is revealed that the radiation energy expenditure for filamentation decreases as the beam radius increases. The peak power in ERT does not exceed the critical self-focusing power for a Gaussian beam during the post-filamentation propagation of a pulse and weakly depends on the initial pulse parameters.

Theory of three-pulse photon echo spectroscopy with dual frequency combs

Jonggu Jeon, JunWoo Kim, Tai Hyun Yoon, and Minhaeng Cho

Doc ID: 368715 Received 31 May 2019; Accepted 30 Sep 2019; Posted 02 Oct 2019  View: PDF

Abstract: A theoretical analysis is carried out for the recently developed three-pulse photon echo spectroscopy employing dual frequency combs (DFC) as the light sources. In this method, the molecular sample interacts with three pulse trains derived from the DFC and the generated third-order signal is displayed as a two-dimensional (2D) spectrum that depends on the waiting time introduced by employing asynchronous optical sampling method. Through the analysis of the heterodyne-detected signal interferogram using a local oscillator derived from one of the optical frequency combs, we show that the 2D spectrum closely matches the spectrum expected from a conventional approach with four pulses derived from a single femtosecond laser pulse and the waiting time between the second and third field-matter interactions is given by the down-converted detection time of the interferogram. The theoretical result is applied to a two-level model system with solvation effect described by solvatochromic spectral density. The model 2D spectrum reproduces spectral features such as the loss of frequency correlation, dephasing, and spectral shift as a function of the population time. We anticipate that the present theory will be the general framework for quantitative descriptions of DFC-based nonlinear optical spectroscopy.

Design and analysis of 6-channel all-optical wavelength filter

Haraprasad Mondal, Mrinal Sen, and Kamanashis Goswami

Doc ID: 374077 Received 29 Jul 2019; Accepted 30 Sep 2019; Posted 02 Oct 2019  View: PDF

Abstract: An all-optical 6-channel wavelength filter has been proposed in this paper, based on a two-dimensional rods-in-air square-lattice photonic crystal (PhC) slab structure. Plane Wave Expansion (PWE) method has been applied to compute the band structure of the PhC. Three-Dimensional Finite Difference Time domain (3D-FDTD) simulation methodology has been used to measure and analyze the performance of the filter. Performances for both the two-dimensional (2D) and three-dimensional (3D) design of the structure have been analyzed. The analyses show that the device is capable of filtering six different wavelengths i.e., 1310 nm, 1415 nm, 1455 nm, 1550 nm, 1725 nm and 1770 nm. Owing to its linear optical operation, the device is able to operate at a low power and, also, offers high data-rate of ~ 2 Tb/s. Moreover, footprint area of the proposed device is in the order of 165 µm2, which is suitable for high density integration of photonic circuits.

A modified Nonlinear Schrödinger Equation for frequency-dependent nonlinear profiles of arbitrary sign

Juan Bonetti, Nicolas Linale, Alfredo Sanchez, Santiago Hernandez, Pablo Fierens, and Diego Grosz

Doc ID: 372983 Received 18 Jul 2019; Accepted 30 Sep 2019; Posted 02 Oct 2019  View: PDF

Abstract: In recent times, materials exhibiting frequency-dependent optical nonlinearities, such as nanoparticle-doped glasses and other metamaterials, have gathered significant interest. The simulation of the propagation of intense light pulses in such media, by means of the nonlinear Schrödinger equation (NLSE), poses the problem that straightforward inclusion of a frequency-dependent nonlinearity may lead to unphysical results; namely, neither the energy nor the photon number are conserved in general. Inspired by a simple quantum-mechanical argument, we derive an energy- and photon-conserving nonlinear Schrödinger equation (pcNLSE). Unlike others, our approach relies only on the knowledge of the frequency-dependent nonlinearity profile and a generalization of Miller's rule for the nonlinear susceptibility, enabling the simulation of nonlinear profiles of arbitrary frequency dependence and sign. Moreover, the proposed pcNLSE can be efficiently solved by the same numerical techniques commonly used to deal with the NLSE. Relevant simulation results supporting our theoretical approach are presented.

Comprehensive focusing analysis of bi-segment spiral zone plate in producing a variety of structured light beams

Arash Sabatyan

Doc ID: 376547 Received 03 Sep 2019; Accepted 30 Sep 2019; Posted 02 Oct 2019  View: PDF

Abstract: This study introduces and demonstrates the diffractive feature of bi-segment spiral zone plate, so each segment has its own width, topological charge and radial phase shift. We show that focusing behavior of this element strongly depends on these parameters. We demonstrate how these features could handle the focused intensity and structure of an incident plane beam. So, a variety of beam shapes and structures are generated at the focal plane. Theoretical and simulations results are verified by the corresponding experiments.

Rational design of colorimetric sensing for customer-oriented index range using plasmonic substrates

Lin Cheng, JIANYONG MAO, Kun Wang, Jiangbo Lu, Kun Huang, Yanpeng Zhang, and Lei Zhang

Doc ID: 374822 Received 06 Aug 2019; Accepted 29 Sep 2019; Posted 02 Oct 2019  View: PDF

Abstract: Both beneficial and harmful matters widely spread in aqueous solutions. Various approaches have been developed to identify them qualitatively and quantitatively. In particular, the colorimetric sensing, relying on an observable environment-induced color change, is a readily accessible approach to detect signals via our naked eyes, with no need of extra optoelectronic devices. Here, we propose a colorimetric sensing scheme with an enhanced performance using plasmonic metasurfaces. By judiciously selecting the structure parameters, the plasmonic resonance can be flexibly tuned at the entire visible range. Along with a pair of polarizers to filter the polarization states of the incident light and output reflection, a plasmonic metasurface, supporting bright colors, can serve as an efficient colorimetric sensing substrate. As an example, a figure of merit can be obtained as high as 1175°/RIU in the demodulation of the hue. Significantly, the sensing capability can be designed according to the selected solvent with a specified refractive index, which promises a target-oriented colorimetric sensing scheme.

Modulational instability in liquid crystals with competing nonlinearities

Shaozhi Pu, Ying Li, Ming Chen, and Liuyang Zhang

Doc ID: 375192 Received 12 Aug 2019; Accepted 29 Sep 2019; Posted 02 Oct 2019  View: PDF

Abstract: We employ a model which is proposed by P. S. Jung et al. [see P. S. Jung et al. Opt. Express 25 (2017) 893- 897] to investigate modulational instability (MI) of plane waves in liquid crystals with competing nonlinearities. We find that the competition between thermal nonlinearity and reorientational nonlinearity leads to unique stability of the plane waves. We also find that both of the nonlocality of the orientational effect (σ1) and the opt-thermal nonlinearity (γ) tend to suppress the MI by decreasing both the gain bandwidth and the maximum gain. Particularly, due to the competing nonlinearities, we find that the MI is closely related to the critical power which is only related to the opt-thermal nonlinearity coefficient (γ) but irrelevant to the profile of the nonlocal response function when σ1=σ2. Interestingly, the plane wave is always stable providing its power larger than the critical power. Our analytical results are confirmed by numerical simulations. These results may provide insight to the theoretical and experimental studies of the solitons in liquid crystals with competing nonlinearities.

A Novel Sinusoidally Modulated Leaky Wave Antenna Based on Cylindrical Graphene Waveguide

Homayoon Oraizi and Hadi Soleimani

Doc ID: 374395 Received 31 Jul 2019; Accepted 29 Sep 2019; Posted 02 Oct 2019  View: PDF

Abstract: Based on the cylindrical graphene waveguide (CGW), the concept and analysis of a novel leaky wave antenna (LWA) at terahertz band are presented. The proposed structure overcomes the limitations of planar LWA characteristics, such as radiation efficiency and beam-width. The values of attenuation and leakage constants can lead to the maximum radiation efficiency and beam-width in the planar LWA equal to about and , but in cylindrical LWA equal to about and , respectively. The leaky wave is excited by a sinusoidally modulated graphene surface (SMGS). A sinusoidally modulated reactance surface (SMRS) allows for a nearly independent control of the phase and leakage constants and thus adjusts the scan angle and radiation efficiency simultaneously. An SMRS was first realized by applying various bias voltages to different gating pads underneath the graphene sheet. Another desirable feature of antenna is the high value of input impedance, so it can easily be matched to a photomixer.

Design of a Radiation-Balanced Fiber-Laser via Optically Active Composite Cladding Materials

Peter Pauzauskie, Xiaojing Xia, Anupum Pant, and E. James Davis

Doc ID: 370585 Received 19 Jun 2019; Accepted 29 Sep 2019; Posted 02 Oct 2019  View: PDF

Abstract: Although the output power of commercial fiber lasers has been reported to exceed 500 kW, the heat generated within fiber gain-media has limited the generation of higher laser powers due to thermal lensing and melting of the gain-media at high temperatures. Radiation balanced fiber lasers promise to mitigate detrimental thermal effects within fiber gain-media based on using upconverted, anti-Stokes photoluminescence to extract heat from the optical fiber’s core. In this manuscript, we experimentally demonstrate that Yb(III) ions within YLiF4 (YLF) crystals are capable of cooling the cladding of optical fibers. We also present a design for radiation-balanced fiber-lasers using a composite fiber cladding material that incorporates YLF nanocrystals as the active photonic heat engine. YLF crystals have the potential to form composite cladding materials to mitigate thermal gradients within the core and cladding based on anti-Stokes photoluminescence. Analytical models of heat transfer within the fiber are presented where the electric-field amplitude within the fiber core is responsible for both the heating of the core, and also the excitation of Yb(III) ions for anti-Stokes laser refrigeration in the cladding.

Brillouin Induced Self-heterodyne Method for Low Jitter Measurement of Laser Linewidth.

Arpita Sinha Roy and Pradeep Kumar Krishnamurthy

Doc ID: 374401 Received 01 Aug 2019; Accepted 27 Sep 2019; Posted 02 Oct 2019  View: PDF

Abstract: In this paper, we study experimentally and analytically the stimulated Brillouin induced self-heterodyne technique for linewidth measurement of lasers having narrow spectral widths. The output of a laser under test (LUT) is modulated by a RF signal to generate the sidebands. The carrier and the sidebands co-propagate in a single-mode fiber (SMF) along withthe stimulated Brillouin scattering (SBS) signal generated by a counter-propagating pump. The SBS process amplifies one of the sidebands, which beats with the LUT carrier wave. The beat signal is detected using a photodiode and analyzed using an electrical spectrum analyzer tocompute the laser linewidth. We analyse the SISH scheme mathematically to obtain expression of the power spectral density of the photocurrent. Experimental results show 20 and 3 dB linewidths of 15 and 5.5 kHz which are in excellent agreement with the estimated theoretical values therebyvalidating the analysis. We also perform the conventional delayed self-heterodyne measurement and obtain 20 dB linewidth of 15 kHz which compares well with SISH method. However, SISH technique reduces jitter by 10 dB. We also study the dependence on linewidth measurement ofthe SISH scheme on fiber length. For 2 km SMF length, the 20 dB linewidth is kHz which is higher compared to the measurement obtained by using 25 km SMF.

On Dyakonov-Voigt surface waves guided by the planar interface of dissipative materials

Chenzhang Zhou, Tom Mackay, and Akhlesh Lakhtakia

Doc ID: 377508 Received 11 Sep 2019; Accepted 26 Sep 2019; Posted 02 Oct 2019  View: PDF

Abstract: Dyakonov--Voigt (DV) surface waves guided by the planar interface of (i) material $\calA$ which is a uniaxial dielectric material, specified by a relative permittivity dyadic with eigenvalues$\eps^s_\calA$ and $\eps^t_\calA$, and (ii) material $\calB$ which is an isotropic dielectric material with relative permittivity $\eps_\calB$, were numerically investigated by solving the corresponding canonical boundary-value problem.The two partnering materials were generally dissipative, with the optic axis of material $\calA$ being inclined at the angle $\chi \in \les 0 ^\circ, 90^\circ \ris$ relative to the interface plane. No solutions of the dispersion equation for DV surface waves exist when $\chi=90^\circ$. Also, no solutions exist for $\chi \in \le 0 ^\circ, 90^\circ \ri$, when both partnering materials are nondissipative.For $\chi \in \les 0 ^\circ, 90^\circ \ri$, the degree of dissipation of material $\calA$ has a profound effect onthephase speeds, propagation lengths, and penetration depths of the DV surface waves. For mid-range values of $\chi$, DV surface waves with negative phase velocities were found. For fixed valuesof $\eps^s_\calA$ and $\eps^t_\calA$ in the upper-half-complex plane, DV surface-wave propagation is only possible for large values of $\chi$ when $| \eps_\calB|$ is very small.

Micro-optics properties of liquid-crystal lens with an arrayed planar non-uniform spiral micro-coil electrode driven by electric-current signals

Mingce Chen, Xinjie Han, Wanwan Dai, Haiwei Wang, Leilei Niu, Qi Shao, Zhang Xinyu, Huiying Wang, and Changsheng Xie

Doc ID: 368183 Received 22 May 2019; Accepted 26 Sep 2019; Posted 02 Oct 2019  View: PDF

Abstract: A new type of electrically controlled liquid-crystal lens (EC-LCL) with an arrayed planar non-uniform spiral micro-coil electrode driven by electric-current signals is proposed. An arrayed cylindrical microbeam focusing and a quasi-circular microbeam focusing corresponding to a circular and an elliptical micro-coil are realized, respectively. Under the control of the electric-current signal with a relatively low intensity, an orderly inclining of LC directors can be achieved through a combined action of the magnetic-field generated by each micro-coil and the magnetic induction electric-field. Through applying different electric-current signals with needed intensity and frequency and dutycycle in a single electrode plate of the LC microcavity, the electrically tunable focusing properties are valuated experimentally, such as an arrayed focal line with ~1.75mm focal length corresponding to a signal voltage of ~45.6Vrms and a focal point with ~2.35mm focal length corresponding to ~55.0Vrms. The researches lay a solid basis for continuously developing the EC-LCL technology.

Surface plasmon resonance sensor for low refractive index detection based on microstructured fiber

jianshuai wang, Li Pei, Ji Wang, Zuliang Ruan, Jingjing Zheng, and Jing Li

Doc ID: 372915 Received 16 Jul 2019; Accepted 24 Sep 2019; Posted 24 Sep 2019  View: PDF

Abstract: A surface plasmon resonance (SPR) sensor based on microstructured fiber (MSF) is proposed for low refractive index (RI) detection in the range of 1.20~1.34. The MSF is composed of substrate and sector air rings with negative curvature. Gold (Au) is coated on the external cladding surface. Finite element method is applied to analyze the performance of the sensor. Results show that the sensor is independent to polarization and the resonance wavelength has a negative shift with RI variation in the near-infrared (near-IR) spectrum. The average sensitivity is -8892 nm/RIU and the maximum resolution is 6.54×10-6. Owing to the high sensitivity in the low RI range, the sensor offers a promising approach for water pollution measuring, humidity monitoring and liquid concentration testing.

High circular dichroism and robust performance in planar plasmonic metamaterial made of nano-comma-shaped resonators

Andrea Veroli, Badrul Alam, Luca Maiolo, Francesco Todisco, Lorenzo Dominici, Milena De Giorgi, Giogio Pattinari, Annamaria Gerardino, and Alessio Benedetti

Doc ID: 373846 Received 26 Jul 2019; Accepted 24 Sep 2019; Posted 25 Sep 2019  View: PDF

Abstract: Circularly dichroic metasurfaces are highly sought for a plethora of applications; while many alternative options are present in literature, it is hard to select an approach that combines high Circular Dichroism (CD) with stable performances and easy reproducibility. In this work we have designed and experimentally investigated a planar plasmonic metamaterial based on a comma-shaped geometry, which features such characteristics. We have focused the complexity of realization in the design process, which combines intrinsic chirality and high field localization, while fabrication was executed by using a standard single-step lift-off procedure. We have produced two classes samples, closely related in shape but differing slightly in designing method and results, both reaching high levels of CD. Experiments on the first reveal the sensitibility of the metasurface to geometrical variations due to fabrication non-idealities, as often happens in metamaterials based on Surface Plasmons and Resonances; on the other hand, with the second we demonstrate that it is possible to guarantee stable peak values on specific wavelength ranges, even when dealing with relevant fabrication tolerances. Moreover, numerical analyses suggest the possibility to reach values converging toward unity. The ease of implementation by using standard fabrication procedures, the robustness of the performance even with fabrication imprecisions make our proposed metamaterial eligible of adoption for further research in high precision spectroscopy and implementation at industrial scale.

Programmable optical waveform generation in mode-locked gain-modulated SOA-fibre laser

Sergey Kobtsev, Boris Nyushkov, Aleksey Ivanenko, and Sergey Smirnov

Doc ID: 369192 Received 03 Jun 2019; Accepted 23 Sep 2019; Posted 24 Sep 2019  View: PDF

Abstract: In this work, we demonstrate for the first time programmable generation of arbitrarily complex optical waveforms in a hybrid synchronously pumped fibre-semiconductor laser. We show that in mode-locked operation, the temporal profile of the generated pulses may follow that of electrical pulses pumping a SOA. Controlling temporal profile of the electrical pump pulses enables formation of a desired amplitude-time pattern of laser pulses reproduced over each cavity round trip. The identified availability of stable periodic optical waveforms with pre-set shape and structure opens up prospects of a new generation of laser radiation sources with widely controllable pulse shape for research and practical applications.

Single-shot laser beam parameters measurement system for near infrared laser beams

Siva Nagisetty, Taisuke Miura, Michal Chyla, Martin Smrz, and Tomas Mocek

Doc ID: 370361 Received 24 Jun 2019; Accepted 23 Sep 2019; Posted 24 Sep 2019  View: PDF

Abstract: We present a simple and fast technique for measuring the laser beam parameters including focus shift using Yaglass®, telecentric lens and camera. Our technique is based on imaging visible fluorescence that represents caustic of the focused near-infrared (NIR) laser beam. By processing single camera frame, great number of second-moment beam diameters are calculated simultaneously without any need for traditional scan in propagation direction. The M2 values measured with this method and standard method are in excellent agreement. We extend this technique to measure the focus shift and focus spot size. This method is fast and allows the real time monitoring of laser beam parameters simultaneously during manufacturing process.

Ultra-broadband and fabrication-tolerant mode (de)multiplexer using subwavelength structure

Weifeng Jiang, Jinye Miao, Tao Li, and Lianhao Ma

Doc ID: 372648 Received 15 Jul 2019; Accepted 21 Sep 2019; Posted 24 Sep 2019  View: PDF

Abstract: An ultra-broadband and fabrication-tolerant mode (de)multiplexer [(De)MUX] is proposed and optimized by inserting the subwavelength gratings (SWGs) into a three-waveguide coupler (TWC). The coupling strength can be dramatically enhanced benefitting from both the SWG and TWC structures. The proposed mode (De)MUX is optimized by using the three-dimensional full-vectorial finite difference time domain based band diagram and propagation analyses. The simulated results indicate that the optimal mode (De)MUX is with a compact coupling length of 14.75 μm, a low loss of 0.3 dB, and a low mode crosstalk of -32.1 dB at the operating wavelength of 1.55 μm. With the mode crosstalk < -15.0 dB, an ultra-broad bandwidth of 369 nm and a relaxed fabrication-tolerance of -43.9 nm to +37.6 nm can be achieved. The 1 dB bandwidth is over 380 nm and the deterioration of the insertion loss is less than 1 dB for a ±50 nm width-change.

Array of Symmetric Nanohole Dimers with High Sensitivity for Detection of Changes in STT-RAM Ultrathin Dielectric Layer

Parinaz Sadri Moshkenani, Mohammad Wahiduzzaman Khan, Md Shafiqul Islam, Ilya Krivorotov, Mikael Nilsson, Nader Bagherzadeh, and Ozdal Boyraz

Doc ID: 364844 Received 11 Apr 2019; Accepted 20 Sep 2019; Posted 24 Sep 2019  View: PDF

Abstract: A dimer nanohole array is proposed for in-situ characterization of radiation damages in STT-RAM multilayer structures. The structure supports a Fano resonance, which is about twice as sensitive to the refractive index changes in surface layer, compared to the plasmonic mode in single nanohole arrays. A simplified STT-RAM multilayer of air/gold(5nm)/MgO(10nm)/gold(60nm)/quartz substrate is considered as the platform for the dimer nanohole array. Our studies show that regarding the changes in the ultrathin MgO layer, the normalized figure of merit for this structure is more than 10 times larger than array of single nanoholes. Furthermore, an improvement of bulk sensing performance over arrays of nanohole heptamers is observed.

Application of dispersion-compensating fiber with W-type refractive index profile in stretcher of ultrashort laser pulses at a wavelength of 1.03 μm

Dmitry Khudyakov, Daniil Ganin, Andrey Lyashedko, Mikhail Likhachev, Andrei Senatorov, Michail Salgansky, and Sergey Vartapetov

Doc ID: 373998 Received 29 Jul 2019; Accepted 19 Sep 2019; Posted 19 Sep 2019  View: PDF

Abstract: The application of a fiber with W-type refractive index profile as a stretcher of ultrashort laser pulses for chirped pulse amplification was shown. As a result the pulses with energy of 3 μJ and duration of 270 fs with high pulse contrast due to dispersion compatibility of the fiber stretcher and compressor on diffraction gratings were obtained. A comparative analysis of several types of fibers for use in stretcher for amplification of chirped pulses in terms of their compatibility with the compressor is given.

The effect of Doppler broadening on giant self-Kerr nonlinearity in a five-level ladder-type system

Khoa Dinh, Bang Nguyen, Doai Le, and Doan Son

Doc ID: 372565 Received 12 Jul 2019; Accepted 17 Sep 2019; Posted 01 Oct 2019  View: PDF

Abstract: In this paper, we propose an analytical model to study the effect of Doppler broadening on self-Kerr nonlinearity in a five-level ladder-type atomic system. First- and third-order susceptibilities and self-Kerr nonlinear coefficient are found as the function of temperature and parameters of laser fields. The analytical model is applied to hot 85Rb and 87Rb atoms and shown that under electromagnetically induced transparency (EIT) effect, self-Kerr nonlinear coefficient is enhanced around three transparent spectral regions. When the temperature of atomic vapor increases (i.e., Doppler width increases), the depth and width of the EIT windows decrease accordingly, and therefore the amplitude of Kerr nonlinear coefficient decreases significantly. In addition, due to the frequency gaps between hyperfine levels of upper exited state 5D5/2 of 85Rb atom is much smaller than those of 87Rb atom, so the EIT windows as well as the nonlinear dispersion curves for 85Rb atom are closer than those for 87Rb atom as the Doppler effect presents. The analytical results agree well with the experimental observation when reducing to three-level atomic system. The analytical model can be used to easily fit the experimental observations of self-Kerr nonlinearity in five-level atomic system under different temperature conditions and apply to related applications in photonic devices.

Femtosecond pulse delivery around 1560 nm in large core inhibited coupling fibers

Dominik Dobrakowski, Anupamaa Rampur, Grzegorz Stepniewski, Dariusz Pysz, Luming Zhao, Yuriy Stepanenko, Ryszard Buczynski, and Mariusz Klimczak

Doc ID: 372842 Received 17 Jul 2019; Accepted 16 Sep 2019; Posted 16 Sep 2019  View: PDF

Abstract: Transmission of ultrashort laser pulses under 100 fs at a central wavelength of 1560 nm from a mode-locked laser is investigated over meter-scale lengths of an inhibited-coupling fiber with 65 µm core diameter. Performance of the fiber in this application is evaluated experimentally using cross-correlation frequency-resolved optical gating, either with the fiber loosely coiled up to 3 m of length or bent over one full loop down to 6 cm radius. Experimental results on observed dispersive stretching of the pulse up to around 200 fs are compared with nonlinear propagation simulations using GNLSE parametrized with measured characteristics of the fiber. Dechirping of the pulse to its original shape in the fiber under bending is observed and related to suppression of higher order modes. We show, that the proposed fiber can be used to transmit around 90 fs long laser pulses without spectral or temporal distortions, if a 6 cm radius loop is applied.

A high-loss and broadband photonic crystal fiber polarization filter with two large apertures coated with gold layers

Xin Yan, Yuanhongliu Gao, Tonglei Cheng, and Shuguang Li

Doc ID: 374749 Received 06 Aug 2019; Accepted 15 Sep 2019; Posted 18 Sep 2019  View: PDF

Abstract: A high-loss and broadband photonic crystal fiber (PCF) polarization filter based on the surface plasma resonance is designed. The designed filter has two large symmetrical holes coated with a metal film. The characteristics of the polarization filter are calculated by the finite element method(FEM).Two pairs of holes near the core are used to obtain high loss. Gold plating in the air holes is used to generate the resonance, which converts a part of the light energy into free-electron vibration energy. The fiber parameters are optimized to achieve specific functions. The proposed filter structure achieves a loss value of 3261.7 dB/cm in the y-direction at 1.31μm, while the loss in the x-direction is very small, and the loss peaks in the x- and y-direction are obviously separated. The thickness of a metal layer and the arrangement and size of air holes near the core are discussed; also, the optimal structure regarding the characteristics of metal-filled polarization filters in photonic crystal fibers is obtained. To the best of our knowledge, this is the first report on a polarization filter than can achieve a loss of up to 3000 dB/cm.

Four-wave mixing of XUV pulses and IR pulses for studies of atomic dynamics

Khuong Dinh, Khoa Anh Tran, Peter Hannaford, and Lap Dao

Doc ID: 373075 Received 18 Jul 2019; Accepted 14 Sep 2019; Posted 16 Sep 2019  View: PDF

Abstract: We apply a cascaded four-wave mixing process in the extreme ultraviolet (XUV) region using two collinear multiple-cycle laser pulses with incommensurate frequencies (wavelengths 1400 and 800 nm) to construct a two-dimensional cross-correlation spectrum. We show that the two-dimensional spectrum can be used to extract the amplitude and phase modifications of the atomic dipole moments of the coupled states in atomic krypton interacting with the intense pulsed laser light. The experimental configuration and a simple model for qualitative interpretation allow us to demonstrate the validity and power of the 2D spectroscopy method in the XUV region.

Optimal condition for optical trapping of large particles: tuning the laser power and numerical aperture of the objective

Nader Reihani and hossein gorjizadeh

Doc ID: 368823 Received 31 May 2019; Accepted 12 Sep 2019; Posted 13 Sep 2019  View: PDF

Abstract: A Gaussian laser beam tightly focused through a high numerical aperture objective lens, so-called Optical tweezers, is widely used for pico-newton range force spectroscopy. Utilizing a proper values for parame- ters such as bead size, numerical aperture of the objective, power of the laser is always a challenge. Here we show which set of the values for the parameters can maximize the lateral trapping efficiency. Our re- sults show that for a high numerical aperture force spectroscopy a bead with a diameter of 4-5μm would be suitable, and that for manipulation using large beads utilizing a proper values for laser power and nu- merical aperture of the objective would be crucial. We present a practical method for choosing the power of the laser that maximizes the lateral trapping efficiency.

Photon avalanche effect in quantum wells: controlling light with light

Aleksei Popov, Andrei Ivanov, and Evgeniy Perlin

Doc ID: 370954 Received 25 Jun 2019; Accepted 12 Sep 2019; Posted 13 Sep 2019  View: PDF

Abstract: A mechanism of controlling the absorption of high-intensity light with the frequency ω and the intensity jω by complementary light with the frequency Ω > 2ω and the two or three orders of magnitude lower intensity jΩ is proposed. The mechanism is based on the photon avalanche effect in quantum wells. The electron concentrations in size quantization subbands and conduction band continuum and the absorbed power of light with the frequency ω are obtained as functions of the intensities jω and jΩ and the time of exposure to laser radiation t. It is established that the resulting dependences exhibit well-pronounced threshold behavior. For example, at jΩ ~ 0.2¬1 kW/cm² and t ~ 0.1¬5 ns, it is possible to control the absorption of high-intensity light ω, so that the absorption of light Ω is practically lacking at intensities jω below the threshold intensity (40¬200 kW/cm²) and becomes very strong at intensities above the threshold intensity. The case when light Ω is the third harmonic of high-intensity light ω is also considered.

Tunable plasmon-induced transparency absorbers based on few-layer black phosphorus ribbon metamaterials

Chao Liu, Hongjian Li, Hui Xu, Mingzhuo Zhao, Cuixiu Xiong, Baihui Zhang, and Kuan Wu

Doc ID: 373534 Received 23 Jul 2019; Accepted 12 Sep 2019; Posted 13 Sep 2019  View: PDF

Abstract: Black phosphorus is a newfangled plasmonic material at the infrared region. We have achieved a mid-infrared plasmon-induced transparency absorption phenomenon via the excitation of black phosphorus surface plasmon using a symmetrical raised ribbon structure. The absorption efficiency can be greatly improved by adding a gold mirror at the bottom of the structure. The relative Fermi level can effectively adjust the absorption efficiency and wavelength. The symmetrical protrusions and ribbon connect to each other and it is beneficial to the operation of the relative Fermi level. After that, the influence of the size of the symmetrical protrusions on absorption characteristics is researched. The results show that the absorption efficiency of the two absorption peaks reaches up to 75%. The angular dependence of the two orientations of the material is used to compare the anisotropy of black phosphorus. This structure can be implemented to realize a mid-infrared modulator, switch controller and absorption device with two prominent functions.

Optomechanically induced transparency and Fano resonances in graphene based nanocavity

Sajid Qamar, Assad Hafiz, Zia uddin, and Muqadder Abbas

Doc ID: 363420 Received 26 Mar 2019; Accepted 03 Sep 2019; Posted 04 Sep 2019  View: PDF

Abstract: We propose a theoretical model to obtain optomechanically induced transparency (OMIT) and Fano resonances in a nanocavity using graphene bilayer as intracavity medium. The motivation comes from an earlier work where Fano resonances have been reported using bilayer graphene [T.-T. Tang, \textit{et al}, Nature Nanotechnology, \textbf{5}, 32 (2010)]. We consider a similar bilayer graphene system, however, inside an optomechanical nanocavity and investigate the effects of different parameters on the output probe field. Here, one mirror of the nanocavity is considered coherently driven by the pump and probe fields whereas second mirror has mechanical oscillation due to the radiation pressure. We consider interaction of bilayer graphene with the optomechanical cavity and show that OMIT and Fano line shapes can be obtained corresponding to output probe field frequency. We notice that OMIT and two Fano resonances can be obtained by manipulated certain parameters, i.e., optomechanical interaction ($g_{mc}$), interaction of G-mode phonon and electronic state ($\lambda_k$), and the coupling between cavity and G-mode phonon ($g_{cp}$). Interestingly, the system exibits OMIT and Fano resonances simultaneously at different probe field frequencies. The accompanying dispersions are very steep and, therefore, extreme slow light can be achieved which can lead to realize optical storage devices and memories. We also notice that OMIT and Fano resonances are very sensitive to the interaction of cavity modes with the oscillating mirror ($g_{mc}$), therefore, due to this enhanced sensitivity, our proposed system can be used to increase the sensitivity of the interferometer \cite{{shi}}. Further, another advantage of using graphene is that it performs better as compared to metals in plasmonic devices.

Optical rectification of ultrafast Yb-lasers: Pushing power and bandwidth of THz generation in GaP

Jakub Drs, Norbert Modsching, Clement Paradis, Christian Kraenkel, Valentin Wittwer, Olga Razskazovskaya, and Thomas Südmeyer

Doc ID: 369518 Received 10 Jun 2019; Accepted 27 Aug 2019; Posted 28 Aug 2019  View: PDF

Abstract: We demonstrate broadband high-power THz generation at MHz repetition rates by optical rectification in GaP driven by an ultrafast Yb-based thin-disk laser oscillator. We investigate the influence of pulse duration in the range of 50 fs to 220 fs and thickness of the GaP crystal on the THz generation. Optimization of these parameters with respect to the broadest spectral bandwidth yields a gap-less THz spectrum extending to nearly 7 THz. We further tailor the driving laser and the THz generation parameters for the highest average power, demonstrating 0.3 mW THz radiation with a spectrum extending to 5 THz. This was achieved using a 0.5 mm thick GaP crystal pumped with a 95 fs, 20 W thin disk laser, operating at 48 MHz repetition rate. We also provide a comprehensive method to estimate the THz spectrum, which can be used for design and optimization of similar THz systems.

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