Accepted papers to appear in an upcoming issue
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Bistable Lasing in Parity-Time Symmetric Coupled Fiber Rings
Sergey Smirnov, Maxim Makarenko, Sergey Suchkov, Dmitry Churkin, and Andrey Sukhorukov
Doc ID: 307530 Received 20 Sep 2017; Accepted 12 Jan 2018; Posted 12 Jan 2018 View: PDF
Abstract: We propose a parity-time (PT) symmetric fiber laser composed of two coupled ring cavities with gain and losses, which operates both in PT-symmetric and broken symmetry lasing depending on the static phase shifts. We perform analytical and numerical analysis by transfer matrix method taking into account gain saturation, and predict laser bistability in the PT-symmetric regime in contrast to a symmetry-broken single-mode operation. In the PT-broken regime, the generation power counter-intuitively increases with an increase of the cavity losses.
Mid-Infrared Silicon Photonic Waveguides and Devices
Yi Zou, Swapnajit Chakravarty, Chi-Jui Chung, Xiaochuan Xu, and Ray Chen
Doc ID: 306245 Received 06 Sep 2017; Accepted 10 Jan 2018; Posted 10 Jan 2018 View: PDF
Abstract: Silicon has been the material of choice of the photonics industry over the last decade due to its easy integration with silicon electronics as well as its optical transparency in the near-infrared and mid-infrared wavelengths. While considerations of micro- and nano-fabrication induced device parameter deviations and a higher than desirable propagation loss still serves as a bottleneck in many data communication applications on chip, applications as sensors do not require similar stringent controls. Photonic devices on chips are increasingly being demonstrated for chemical and biological sensing with performance metrics rivaling benchtop instruments and thus promising the potential of portable, handheld and wearable monitoring of various chemical and biological analytes. In this paper, we review recent advances in mid-infrared (MIR) silicon photonics research. We discuss the pros and cons of various platforms, the fabrication procedure for building such platforms, the benchmarks demonstrated so far, together with their applications. Novel device architectures and improved fabrication techniques have paved a viable way for realizing low-cost, high density, multi-function integrated devices in the MIR. These advances are expected to benefit several application domains in the years to come, including communication networks, sensing, and nonlinear systems.
Improved common-path spectral interferometer for single-shot terahertz detection
Shuiqin Zheng, QINGGANG LIN, Yi Cai, Xuanke Zeng, Ying Li, Shixiang Xu, Jingzhen Li, and Dianyuan Fan
Doc ID: 319065 Received 05 Jan 2018; Accepted 08 Jan 2018; Posted 10 Jan 2018 View: PDF
Abstract: To seek high SNR is critical but challenging for single-shot intense terahertz (THz) coherent detection. This paper presents improved common-path spectral interferometer for single-shot terahertz detection with a single chirped pulse as the probe for THz electro-optic (EO) sampling. Here, the spectral interference occurs between the two orthogonal polarization components with a required relative time delay generated with only a birefringent plate after the EO sensor. Our experiments show this interferometer can effectively suppress the noises usually suffering in a non-common-path interferometer. The measured single-shot SNR is up to 88.85. And the measured THz waveforms are independent of the orientation of the used ZnTe EO sensor, so it is easy to operate it and the results are more reliable. These features mean that the interferometer is quite qualified for the applications where the strong THz pulses, usually with single-shot or low repetition rate, are indispensable.
End-fire coupling of surface plasmon polaritons in a metal-insulator-metal waveguide using simple photoplastic connector
Yevhenii Morozov, Anatoliy Lapchuk, Minglei Fu, Andriy Kryuchyn, Haoran Huang, and Zichun Le
Doc ID: 306279 Received 04 Sep 2017; Accepted 02 Jan 2018; Posted 03 Jan 2018 View: PDF
Abstract: We propose a design of efficient end-fire coupling of surface plasmon polaritons in a metal-insulator-metal (MIM) waveguide with an optical fiber as a part of simple photoplastic connector. Detailed analysis and optimization of the design were performed by the finite-difference time domain method. The calculated value of excitation efficiency coefficient of the MIM waveguide is equal to 83.7% (–0.77 dB) at the light wavelength of 405 nm. This design allows one to perform simple connection of an optical fiber to MIM waveguides and makes it possible to locally excite them with high energy efficiency. Besides, usage of the design allows reducing the length of metallic elements of the MIM waveguides and, therefore, reducing the dissipative losses. In summary, the proposed design can be of practical importance in plasmonic-type waveguide applications, like as near-field investigation of live cells and other objects features with a super-resolution.
Tuning the metal filling fraction in metal-insulator-metal ultra-broadband perfect absorbers to maximize the absorption bandwidth
Amir Ghobadi, Hodjat Hajian, Alireza Rahimi Rashed, Bayram Butun, and Ekmel Ozbay
Doc ID: 314284 Received 24 Nov 2017; Accepted 29 Dec 2017; Posted 03 Jan 2018 View: PDF
Abstract: In this article, we propose a methodology to maximize the absorption bandwidth (BW) of a metal-insulator-metal (MIM) based absorber. The proposed structure is made of a Cr-Al2O3-Cr multilayer design. At the initial step, the optimum MIM planar design is fabricated and optically characterized. The results show absorption above 0.9 from 400 nm to 850 nm. Afterward, the transfer matrix method (TMM) is used to find the optimal condition for the perfect light absorption in an ultra-broadband frequency range. This modeling approach predicts that changing the filling fraction (FF) of the top Cr layer can extend light absorption toward longer wavelengths. We experimentally proved that the use of proper top Cr thickness and annealing temperature leads to a nearly perfect light absorption from 400 nm to 1150 nm that is much broader than that of a planar design. Therefore, while keeping the overall process lithography-free, the absorption functionality of the design can be significantly improved. The results presented here can serve as a beacon for future performance enhanced multilayer designs where a simple fabrication step can boost the overall device response without changing its overall thickness and fabrication simplicity.
Cylindrical vector beams excited tunable second harmonic generation in a plasmonic octamer
Fajun Xiao, Wuyun Shang, Weiren Zhu, lei han, Malin Premaratne, Ting Mei, and Jianlin Zhao
Doc ID: 309785 Received 24 Oct 2017; Accepted 28 Dec 2017; Posted 03 Jan 2018 View: PDF
Abstract: We report a method to tune the second harmonic generation (SHG) frequency of a metallic octamer by employing cylindrical vector beams as the excitation. Our method exploits the ability to spatially match the polarization state of excitations and the dipole moment of plasmonic modes to excite the target dark modes, enabling a tunable resonance band of field enhancement. Since the SHG intensity is proportional to the square of the fundamental field intensity, the resonance frequency of SHG can be tuned over a broad bandwidth in excess of 400 nm by changing the excitation from a linear polarized Gaussian beam to a radially and azimuthally polarized beam.
X-ray absorption spectroscopy study of energy transport in foil targetsheated by PW laser pulses
Igor Skobelev, Sergey Ryazantsev, Denis Arich, Pavel Bratchenko, Anatoly Faenov, Tatiana Pikuz, Phill Durey, Leo Doehl, Damon Farley, Christopher Baird, Kate Lancaster, christopher murphy, Nicola Booth, Christopher Spindloe, Paul McKenna, Stephanie Hansen, James Colgan, Ryosuke Kodama, Nigel Woolsey, and Sergey Pikuz
Doc ID: 313362 Received 13 Nov 2017; Accepted 27 Dec 2017; Posted 03 Jan 2018 View: PDF
Abstract: Absorption x-ray spectroscopy is proposed as a method for studying the heating of a solid-density matter excited by secondary x-ray radiation from a relativistic laser-produced plasma. The method was developed and applied to experiments involving thin silicon foils irradiated by 0.5–1.5 ps duration ultrahigh contrast laser pulses at intensities between 0.5×1020 and 2.5×1020 W/cm2. The electron temperature of the material at the rear side of a target is estimated to be in the range of 140–300 eV. The diagnostic approach enables the diagnosis of warm dense matter states with low self-emissivity.
Enhancement of the phase conjugation degenerate four-wave mixing using the Bessel beam
qian zhang, xue cheng, Haowei Chen, Bo He, Zhaoyu Ren, Ying Zhang, and Jintao Bai
Doc ID: 310019 Received 26 Oct 2017; Accepted 22 Dec 2017; Posted 03 Jan 2018 View: PDF
Abstract: We report on the enhancement of phase conjugation degenerate four-wave mixing (DFWM) in the hot atomic Rb vapor by using Bessel beam as the probe beam. The Bessel beam was generated using cross-phase modulation based on thermal nonlinear optical effect. Our results demonstrated that the DFWM signal generated by the Bessel beam is about twice larger than that generated by Gaussian beam, which can be attributed to the extended depth and tight focusing features of the Bessel beam. We also found that DFWM signal with reasonable intensity can be detected even when the Bessel beam encounters an obstruction on its way, thanks to the self-healing property of the Bessel beam. This work not only indicates that DFWM using the Bessel beam would be of great potential in the fields of high-fidelity communication, adaptive optics and so on, but also suggests that the Bessel beam would be of significance to enhance the nonlinear process, especially in those thick and scattering medium.
All-optical switching in Si photonic waveguides with epsilon-near-zero resonant cavity
Andres Neira, Gregory Wurtz, and Anatoly Zayats
Doc ID: 305271 Received 05 Sep 2017; Accepted 20 Dec 2017; Posted 22 Dec 2017 View: PDF
Abstract: Strong nonlinearity of plasmonic metamaterials can be designed near their effective plasma frequency in the epsilon near-zero (ENZ) regime. We explore the realization of an all-optical modulator based on the Au nonlinearity using an ENZ cavity formed by a few Au nanorods inside Si photonic waveguide. The resulting modulator has a robust performance with a modulation depth of about 30 dB/m and loss less than 0.8 dB at the switching energy below 600 fJ. The modulator provides a double advantage of high mode transmission and strong nonlinearity enhancement in the few nanorod-based design.
Sharp tunable and additional-noise-free optical filter based on Brillouin losses
Cheng Feng, Stefan Preussler, and Thomas Schneider
Doc ID: 312692 Received 03 Nov 2017; Accepted 20 Dec 2017; Posted 22 Dec 2017 View: PDF
Abstract: In this paper, we propose an additional-noise-free, independent center frequency and bandwidth tunable optical filter based on stimulated Brillouin scattering (SBS) losses. By suppressing the out-of-band signal with two broadened symmetric SBS losses, tunable pass bandwidths from 500 MHz to 9.5 GHz and the independent center frequency tunability are demonstrated. Considering the limited SBS interaction in the center frequency range, a flat-top response with only 0.3 dB ripple is easily achieved. Assisted by the extra suppression from polarization pulling, a selectivity of more than 20 dB and an ultra-high 250 dB/GHz roll-off are reached. A gain based SBS filter adds noise to the filtered signal. However, for our proposed filter setup no additional noise is detected due to the transparency in the passband. Considering the wide independent bandwidth and center frequency tunability, flat-top response, and low-noise characteristic, our proposed filter can be perfectly used as a supplement of most commercialized tunable optical single bandpass filters, whose minimum bandwidth is limited by 10 GHz.
Single-Mode VCSEL for Pre-Emphasis PAM-4 transmission up to 64 Gbit/s over 100-300 m in OM4 MMF
Hsuan-Yun Kao, Cheng-Ting Tsai, Shan-Fong Leong, Chun-Yen Peng, Yu-Chieh Chi, Huai-Yung Wang, Hao-chung Kuo, Chao-Hsin Wu, Wood-Hi Cheng, and Gong-Ru Lin
Doc ID: 312994 Received 08 Nov 2017; Accepted 17 Dec 2017; Posted 22 Dec 2017 View: PDF
Abstract: A single-mode vertical cavity surface emitting laser (VCSEL) based data transmission is demonstrated, which enables 4-level pulse amplitude modulation (PAM-4) at 64 Gbit/s over 100-300 m in the OM4 multi-mode fiber (MMF). By optimizing the bias of the single-mode VCSEL with a differential resistance of 159 ohm the related electrical return loss of -5.7 dB is evaluated to provide an analog modulation bandwidth of 18.9 GHz. After pre-emphasizing waveform of the PAM-4 format, the PAM-4 data stream can be successfully delivered by the single-mode VCSEL at 64 Gbit/s under back-to-back and 100-m-long OM4 MMF conditions. Lengthening the transmission distance worsens the signal-to-noise ratio of PAM-4 data to the FEC criterion, as the waveform pre-emphasis of the PAM-4 data stream inevitably induces spectral power compensation from-low to high frequencies. Therefore, increasing the OM4 MMF distance from 200 to 300 m significantly reduces the peak-to-peak amplitude of data to suppress the SNR and reduce the transmission capacity from 52 to 48 Gbit/s.
Dispersive non-Hermitian optical heterostructures
Oksana Shramkova, Konstantinos Makris, G. Tsironis, and Demetrios Christodoulides
Doc ID: 304978 Received 25 Aug 2017; Accepted 13 Dec 2017; Posted 15 Dec 2017 View: PDF
Abstract: The effect of material dispersion on the optical properties of one-dimensional non-Hermitian scattering systems is investigated in detail. In particular, multilayer heterostructures with gain and loss (PT-symmetric or not) are examined by taking into account the dispersion of every layer. The exceptional points, and phase transitions are characterized based on the spectrum of the corresponding scattering matrix. We demonstrate that an on-average lossy heterostructure can amplify an incident plane wave at a frequency range associated with the emission frequency of the layer with gain.
Parity-time-symmetric whispering-gallery-mode nanoparticle sensor
Weijian Chen, Jing Zhang, Bo Peng, Sahin Ozdemir, Xudong Fan, and Lan Yang
Doc ID: 309078 Received 12 Oct 2017; Accepted 13 Dec 2017; Posted 15 Dec 2017 View: PDF
Abstract: We present a study of single nanoparticle detection using parity-time (PT)-symmetric whispering-gallery mode (WGM) resonators. Our theoretical model and numerical simulations show that with balanced gain and loss, the PT-symmetric WGM nanoparticle sensor, tailored to operate at the PT phase transition points (also called exceptional points), exhibits significant enhancement in frequency splitting when compared to a single WGM nanoparticle sensor subject to the same perturbation. The presence of gain in the PT-symmetric system leads to narrower linewidth, which helps to resolve smaller changes in the frequency splitting and improve detection limit of nanoparticle sensing. Furthermore, we also provide a general method for detecting multiple nanoparticles entering the mode volume of a PT-symmetric WGM sensor one by one. Our study shows the feasibility of PT-symmetric WGM resonators for ultrasensitive single nanoparticle and biomolecule sensing.
Valence state manipulation of Sm3+ ions via a phase-shaped femtosecond laser field
Ye Zheng, Yunhua Yao, Lianzhong Deng, Wen Cheng, Jianping Li, Tianqing Jia, Jianrong Qiu, Zhenrong Sun, and shi zhang
Doc ID: 309766 Received 24 Oct 2017; Accepted 12 Dec 2017; Posted 19 Dec 2017 View: PDF
Abstract: The ability to manipulate the valence state conversion of rare-earth ions is crucial for their applications in color display, optoelectronic device, laser source and optical memory. The conventional femtosecond laser pulse has shown to be a well-established tool to realize the valence state conversion of rare-earth ions, whereas the valence state conversion efficiency is relatively low. Here, we first propose a femtosecond laser pulse shaping technique to improve the valence state conversion efficiency of rare-earth ions. Our experimental results demonstrate that the photo-reduction efficiency from Sm3+ to Sm2+ in the Sm3+-doped sodium aluminoborate glass by a π phase step modulation can be comparable to that by the transform-limited femtosecond laser field, while the peak laser intensity is decreased by about 60%, which is very beneficial for improving the valence state conversion efficiency under the laser-induced damage threshold of glass sample. Furthermore, we also theoretically develop a (2+1) resonance-mediated three-photon absorption model to well explain the modulation of photo-reduction efficiency from Sm3+ to Sm2+ under the π-shaped femtosecond laser field.
Optical forces of focused femtosecond laser pulses on nonlinear optical Rayleigh particles
Liping Gong, Gu Bing, Guanghao Rui, Yiping Cui, Zhuqing Zhu, and Qiwen Zhan
Doc ID: 311249 Received 30 Oct 2017; Accepted 11 Dec 2017; Posted 15 Dec 2017 View: PDF
Abstract: The principle of optical trapping is conventionally based on the interaction of optical fields with linear induced polarizations. However, the optical force originating from the nonlinear polarization becomes significant when nonlinear optical nanoparticles are trapped by femtosecond laser pulses. Herein we develop the time-averaged optical forces on a nonlinear optical nanoparticle using high-repetition-rate femtosecond laser pulses, based on the linear and nonlinear polarization effects. We investigate the dependence of the optical forces on the magnitudes and signs of the refractive nonlinearities. It is found that the self-focusing effect enhances the trapping ability, whereas the self-defocusing effect leads to the splitting of potential well at the focal plane and destabilizes the optical trap. Our results show good agreement with the reported experimental observations and provide a theoretical support for capturing nonlinear optical particles.
Terahertz Emission from Localized Modes in One-Dimensional Disordered Systems
Yongquan Zeng, Liang Guozhen, Bo Qiang, Bo Meng, Houkun Liang, shampy mansha, Jianping Li, Zhaohui Li, Lian He Li, Giles Davies, Edmund Linfield, Ying Zhang, Yidong Chong, and Qijie Wang
Doc ID: 308909 Received 03 Nov 2017; Accepted 11 Dec 2017; Posted 11 Dec 2017 View: PDF
Abstract: We demonstrate terahertz (THz) frequency laser emission around 3.2 THz from localized modes in one-dimensional (1D) disordered grating systems. The disordered structures are patterned on top of the double-metal waveguide of a THz quantum cascade laser. Multiple emission peaks are observed within a frequency range corresponding to the bandgap of a periodic counterpart with no disorder, indicating the presence of mode localization aided by Bragg scattering. Simulations and experimental measurements provide strong evidence for the spatial localization of the THz laser modes.
Diode-pumped power scalable Kerr-lens mode-locked Yb:CYA laser
Wenlong Tian, Yingnan Peng, Ziyue Zhang, Zijiao Yu, Jiangfeng Zhu, Xiaodong Xu, and Zhiyi Wei
Doc ID: 309535 Received 20 Oct 2017; Accepted 11 Dec 2017; Posted 11 Dec 2017 View: PDF
Abstract: Stable 68-fs pulses with the average power of 1.5 W is directly generated from a multi-mode diode-pumped Kerr-lens mode-locked Yb:CYA laser by separating the gain medium and Kerr medium. The repetition rate is about 50 MHz, resulting in a single pulse energy of 30 nJ and a peak power of 0.44 MW. To the best of our knowledge, this is the highest single pulse energy ever produced from a mode-locked Yb:CYA oscillator. Our experimental results show that Yb:CYA crystal is an excellent candidate for multi-watt, sub-100 fs pulse generation in diode-pumped all-solid-state lasers. It is believed that the output power can be scalable to multi-W while maintaining the pulse duration with this simple method.
Silicon Intensity Mach-Zehnder Modulator for Single Lane 100 Gb/s applications
miaofeng li, Lei Wang, xiang li, Xi Xiao, and Shaohua Yu
Doc ID: 309808 Received 27 Oct 2017; Accepted 10 Dec 2017; Posted 11 Dec 2017 View: PDF
Abstract: In this paper, substrate removing technique in silicon Mach-Zehnder modulator (MZM) is proposed and demonstrated to improve the modulation bandwidth. Based on the novel and optimized traveling wave electrodes, the electrode transmission loss is reduced and the electro-optical group index and 50-ohm impedance matching are improved, simultaneously. A 2 mm long substrate removed silicon MZM with the measured and extrapolated 3 dB electro-optical bandwidth of >50 GHz and 60 GHz at the -8 V bias voltage is designed and fabricated. Open optical eye diagrams of up to 90 Gbaud/s NRZ and 56 Gbaud/s four-level pulse amplitude modulation (PAM-4) are experimentally obtained without additional optical or digital compensations. Based on this silicon MZM, the performance in a short-reach transmission system is further investigated. Single-lane 112 Gb/s and 128 Gb/s transmissions over different distances of 1 km, 2 km and 10 km are experimentally achieved based on this high-speed silicon MZM.
Enhanced optical and thermal performance of white light emitting diodes with horizontally-layered quantum dots phosphor nanocomposite
Shudong Yu, Yong Tang, Zongtao li, Kaihang Chen, Xinrui Ding, and Binhai Yu
Doc ID: 305830 Received 28 Aug 2017; Accepted 07 Dec 2017; Posted 11 Dec 2017 View: PDF
Abstract: In this paper, we propose a novel packaging scheme with horizontally-layered quantum dots (QDs) phosphor nanocomposites to obtain an enhanced optical and thermal performance for white light emitting diodes (WLEDs). Three different WLEDs, including QDs-phosphor mixed type, QDs-outside type and QDs-inside type, are fabricated and compared. When the phosphor and QDs concentrations are respectively 30% and 0.15%, the QDs-outside type shows the best optical performance with a luminous efficiency (LE) of 71.6 lm/W@400 mA, Ra=85.5 and R9=80.8 compared to the mixed type with LE=58.8 lm /W, Ra=84.7 and R9=48.6 and the QDs-inside type with LE=37.3 lm/W and no Ra or R9. As regards the maximum nanocomposite and QDs temperature, the QDs-outside type has the lowest values (64.2/51.1℃) compared with the mixed type (88.0/88.0℃) and the QDs-inside type (96.6/96.6℃). The excellence of QDs-outside type is due to the reduced re-absorption between yellow phosphor and red QDs and high energy transfer efficiency between excitation light and QDs phosphor nanocomposite.
Single nanoparticle trapping based on on-chip nanoslotted nanobeam cavities
Daquan Yang, Fei Gao, Qi-Tao Cao, Chuan Wang, Yuefeng Ji, and Yun-Feng Xiao
Doc ID: 306327 Received 04 Sep 2017; Accepted 06 Dec 2017; Posted 07 Dec 2017 View: PDF
Abstract: Optical trapping techniques have been of great interest and advantages that enable the direct handling of nanoparticles. Among various optical trapping systems, photonic crystal nanobeam cavities have attractedgreat attentions for integrated on-chip trapping and manipulation. However, the optical trapping with high efficiency and low input power is still a big challenge in nanobeam cavities, because most of light energy isconfined within the solid dielectric region. To this end, by incorporating a nanoslotted structure into an ultracompact one dimensional photonic crystal nanobeam cavity structure, we design a promising on-chip devicewith ultralarge trapping potential depth to enhance optical trapping characteristic of the cavity. In this work, we firstly provide systematic analysis of the optical trapping force for a polystyrene (PS) nanoparticle trapped in a cavity model. Then, to validate the theoretical analysis, the numerical simulation proof is demonstrated in detail by using three dimensional finite element method. For trapping a PS nanoparticle of 10nm radius within the slot, the maximum trapping force as high as 8.28nN/mW and the depth of trapping potential as large as 1.15×10⁵k_BT/mW are obtained, respectively. Moreover, the threshold power for stable trapping aslow as 0.087µW is achieved, more than two orders of magnitude decreased compared to previous designs. In addition, trapping of single 25nm radius PS nanoparticle causes a 0.6nm red-shift in peak wavelength. Thus, the proposed cavity device can be used to realize the detection of single nanoparticle trapping by monitoring the resonant peak wavelength shift. We believe that the architecture with features of ultra-compact footprint,high integrability with optical waveguides/circuits and efficient trapping demonstrated here will be a promising candidate for developing lab-on-a-chip device with versatile functionalities.
30 W monolithic 2-3 μm supercontinuum laser
Ke Yin, Bin Zhang, Linyong Yang, and Jing Hou
Doc ID: 308552 Received 04 Oct 2017; Accepted 06 Dec 2017; Posted 07 Dec 2017 View: PDF
Abstract: A high-power all-fiber supercontinuum (SC) laser source based on germania-core fiber (GCF) was presented. The less absorption loss of GCF than silica fiber beyond 2.0 μm made it more suitable for extending the SC spectrum to the long wavelength side. In this work, the GCF based SC laser had a maximum power of 30.1 W, together with a 10 dB spectral bandwidth of >1000 nm spanning from 1.95 to 3.0 μm. To the best of the our knowledge, this was the highest output power level ever reported for a GCF based SC laser as well as a 2-3 μm SC laser.
Passively mode-locked Er-doped fiber laser based on SnS2 nanosheets as saturable absorber
kangdi niu, Ruyi Sun, qingyun chen, Baoyuan Man, and huanian Zhang
Doc ID: 305245 Received 21 Aug 2017; Accepted 05 Dec 2017; Posted 06 Dec 2017 View: PDF
Abstract: In this letter, to our knowledge, Tin disulfide (SnS2), a two-dimensional n-type direct bandgap transition metal dichalcogenide with a gap value of 2.24 eV, was employed as saturable absorber for the first time. Its appearance and nonlinear saturable absorption characteristics were also investigated experimentally. SnS2-PVA film is successfully prepared and employed as mode-locker for achieving an Er-doped fiber laser with a pulse width of 6 fs at a pulse repetition rate of 29.33 MHz. The results prove that SnS2 nanosheets will have wide potential ultrafast photonic and optoelectronic applications due to its suitable bandgap value and excellent nonlinear saturable absorption characteristics.
Bionic SERS chip with super-hydrophobic and plasmonic micro-nano dual structure
Fengyou Yang, Haoran Zhang, Huimin Feng, Jianjie Dong, Chuang Wang, and Qian Liu
Doc ID: 306750 Received 12 Sep 2017; Accepted 05 Dec 2017; Posted 06 Dec 2017 View: PDF
Abstract: Natural surface-enhanced Raman spectroscopy (SERS) chips based on plant or insect have been increasingly concerned due to their facile characteristic and low cost. However, such chips remain a big challenge for practical application because of poor reproducibility and stability as well as unavoidable damage to the surface structure during coating metal and uncontrolled dehydration. By using a very simple wrinkling method, we develop a new route to fabricate low-cost bionic SERS chip for practical detection. Inspired by taro leaf, we fabricate a SERS chip with super-hydrophobic and plasmonic micro-nano dual structure, and its structure parameters can be optimized. Compared to the natural taro-leaf SERS chip, our artificial chip exhibits an order of magnitude higher performance of R6G detection in both sensitivity (~ 10-⁹ M) and enhancement factor (~ 10⁷) of Raman signal under weak-laser illumination, demonstrating our SERS chip has a great potential in biological detection. These excellent performances of our bionic SERS chip are attributed to a synergy of optimized micro-wrinkle and nano-nest, which is verified by both contrast experiment and FDTD simulation. We believe our bionic chip is a promising candidate in practical application due to its merits such as simple fabricating process, optimizable structure, low cost, excellent homogeneity, high sensitivity and stability.
Surface-enhanced Raman scattering on dielectric microspheres with whispering gallery mode resonance
Steven Huang, Xuefeng Jiang, Bo Peng, Corey Janisch, Alexander Cocking, Sahin Ozdemir, Zhiwen Liu, and Lan Yang
Doc ID: 308983 Received 23 Oct 2017; Accepted 05 Dec 2017; Posted 06 Dec 2017 View: PDF
Abstract: Conventionally, metallic nanostructures are used for Surface-Enhanced Raman Spectroscopy (SERS), but recently there has been increasing interest in the enhancement of Raman scattering from dielectric substrates due to their improved stability and biocompatibility compared with metallic substrates. Here, we report the observation of enhanced Raman scattering from rhodamine 6G molecules coated on silica microspheres. We excite the Whispering-Gallery-Modes (WGMs) supported in the microspheres with tapered fiber coupler for efficient WGM excitation, and the Raman enhancement can be attributed to the WGM mechanism. Strong resonance enhancement in pump laser intensity and modified Raman emission from Purcell effect in the microsphere resonator are observed from experiment and compared with theoretical results. A total Raman enhancement factor of 1.4 × 10⁴ is observed, with contribution mostly from the enhancement in pump laser intensity. Our results show that with an efficient pumping scheme, dielectric microspheres are a viable alternative to metallic SERS substrates.
Photon-Pair Generation in Quadratically Nonlinear PT-Symmetric Coupler
Diana Antonosyan, Alexander Solntsev, and Andrey Sukhorukov
Doc ID: 306913 Received 12 Sep 2017; Accepted 29 Nov 2017; Posted 30 Nov 2017 View: PDF
Abstract: Integrated nonlinear waveguide structuresenable generation of quantum entangled photons.We describe theoretically the effects of spatially inhomogeneous loss on thecreation of photon pairs through spontaneous parametric down-conversion in quadratically nonlinear directional couplers, where photons experiences effective parity-time (PT) symmetric potential due to presence of optical loss in one of the waveguides. We show that for losses below PT-breaking threshold, the quantum photon states can be flexibly tuned similar to conservative couplers, whereas for stronger losses the correlations between two waveguide modes are suppressed. We also formulate a quantum-classical correspondence with sum-frequency generationfor fast evaluation of device performance.These results can be applied for the design of quantum plasmonic circuits.
Effect of anti-crossings with cladding resonances on ultrafast nonlinear dynamics in gas-filled PCFs
Francesco Tani, Felix Köttig, David Novoa, Ralf Keding, and Philip Russell
Doc ID: 307635 Received 22 Sep 2017; Accepted 21 Nov 2017; Posted 21 Nov 2017 View: PDF
Abstract: Spectral anti-crossings between the fundamental guided mode and core wall resonances alter the dispersion in hollow-core anti-resonant-reflection photonic crystal fibers. Here we study the effect of this dispersion change on the nonlinear propagation and dynamics of ultrashort pulses. We find that it causes emission of narrow spectral peaks through a combination of four-wave mixing and dispersive wave emission. We further investigate the influence of the anti-crossings on nonlinear pulse propagation and show that their impact can be minimized by adjusting the core-wall thickness in such a way that the anti-crossings lie spectrally distant from the pump wavelength.