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Deep Plug-and-Play Priors for Spectral Snapshot Compressive Imaging

Siming Zheng, Yang Liu, Ziyi Meng, Mu Qiao, Zhishen Tong, Xiaoyu Yang, Shensheng Han, and Xin Yuan

DOI: 10.1364/PRJ.411745 Received 05 Oct 2020; Accepted 23 Nov 2020; Posted 23 Nov 2020  View: PDF

Abstract: We propose a plug-and-play (PnP) method, which uses deep-learning-based denoisers as regularization priors for spectral snapshot compressive imaging (SCI). Our method is efficient in terms of reconstruction quality and speed trade-off, and flexible to be ready-to-use for different compressive coding mechanisms. We demonstrate the efficiency and flexibility in both simulations and five different spectral SCI systems and show that the proposed deep PnP prior could achieve state-of-the-art results with a simple plug-in based on the optimization framework. This paves the way for capturing and recovering multi- or hyper-spectral information in one snapshot, which might inspire intriguing applications in remote sensing, biomedical science and material science.

Programme controlled single soliton microcomb source

Xinyu Wang, Peng Xie, Weiqiang Wang, yang wang, zhizhou lu, Leiran Wang, Brent Little, Wei Zhao, Wenfu Zhang, and Sai Chu

DOI: 10.1364/PRJ.408612 Received 27 Aug 2020; Accepted 22 Nov 2020; Posted 22 Nov 2020  View: PDF

Abstract: Soliton microcombs (SMCs) are spontaneously formed in a coherently pumped high-quality microresonator, which have significant application values in science and technology. However, the generation of SMCs seriously relies on advanced experimental techniques from professional scientists, which limits its application potential and promotion. Here, we experimentally demonstrate a programme controlled single SMC source where the intracavity thermal effect is timely balanced using an auxiliary laser during single SMC generation. The microcomb power is adopted as the criteria for microcomb states discrimination and a forward and backward thermal tuning technique is employed for the deterministic single SMC generation. Single SMC can be automatically formed in ~80 seconds and the reliability of our scheme is verified by consecutive 200 single SMC generation trails. The “one-button start” SMC source would have significant promising influences in future SMC based application development.

An optical frequency synthesizer referenced to an ytterbium optical clock

yuan yao, Bo Li, Guang Yang, chen tong, Yaqin Hao, Hongfu Yu, Yanyi Jiang, and Long-Sheng Ma

DOI: 10.1364/PRJ.409534 Received 15 Sep 2020; Accepted 22 Nov 2020; Posted 22 Nov 2020  View: PDF

Abstract: Optical clocks with unprecedented accuracy of 10^(−18) promise innovations in precision spectroscopy and measurement. To harness the full power of optical clocks, we need optical frequency synthesizers (OFS) to accurately convert the stabilities and accuracies of optical clocks to other desired frequencies. This work demonstrates such an OFS referenced to an ytterbium optical clock, employing an accurate optical frequency divider (OFD) to realize conversion. It is based on an optical frequency comb stabilized to a commercial rubidium frequency standard, in this way most combs can operate robustly. Despite of comb frequency instability at 10^(−11), the division noise and uncertainty of the OFD reach 6 × 10^(−18) (1 s) and 5 × 10^(−21) respectively, facilitating frequency synthesis of the best optical clocks. With the OFD, the frequency of the OFS reference laser at 1064 nm is accurately divided to a 578 nm laser for resolving Hz-level linewidth ytterbium clock transition (unaffected by MHz-linewidth comb lines) and faithfully locking the OFS to ytterbium optical clock.

Integrating deep learning to achieve phase compensation for free space orbital angular momentum-encoded quantum key distribution under atmospheric turbulence

xingyu wang, Terry Wu, Dong Chen, Haonan Zhu, and ShangHong Zhao

DOI: 10.1364/PRJ.409645 Received 09 Sep 2020; Accepted 20 Nov 2020; Posted 22 Nov 2020  View: PDF

Abstract: A high-dimensional quantum key distribution (QKD), which adopts degrees of freedom of the orbital angular momentum (OAM) states, is beneficial to realize secure and high speed QKD. However, the helical phase of a vortex beam which carries OAM is sensitive to the atmospheric turbulence and easy to be distorted. In this paper, an adaptive compensation method using deep learning technology is developed to improve the performance of OAM-encoded QKD system. A convolutional neural network (CNN) model is first trained to learn the mapping relationship of intensity profiles of inputs and the turbulent phase, and such the mapping is used as feedback to control a spatial light modulator to generate phase screen for correcting the distorted vortex beam. Then, a OAM-encoded QKD scheme with the capability of real-time phase correction is designed, in which the compensation module only needs extract the intensity distributions of Gaussian probe beam and thus ensure that the information encoded on OAM states would not be eavesdropped. The results show that, our method can efficiently improve the mode purity of the encoded OAM states and extend the secure distance for the involved QKD protocols in the free-space channel, which is not limited to any specific QKD protocol.

Parametric oscillation of electromagnetic waves in momentum band gaps of a spatiotemporal crystal

Seo-Joo Lee, Jagang Park, Hyukjoon Cho, Bumki Min, Yifan Wang, Brian Kim, and Chiara Daraio

DOI: 10.1364/PRJ.406215 Received 24 Aug 2020; Accepted 19 Nov 2020; Posted 22 Nov 2020  View: PDF

Abstract: Photonic crystals have revolutionized the field of optics with their unique capabilities of dispersion and energy band gap engineering, such as the demonstration of extreme group and phase velocities, topologically-protected photonic edge states, and the control of spontaneous emission of photons. Time-variant media have also shown distinct functionalities including nonreciprocal propagation, frequency conversion, and amplification of light. However, spatiotemporal modulation has mostly been studied as a simple harmonic wave function. Here, we analyze time-variant and spatially-discrete photonic crystal structures, referred to as spatiotemporal crystals. The design of spatiotemporal crystals allows the engineering of momentum band gap, within which parametric amplification can occur. As a potential platform for the construction of a parametric oscillator, a finite-sized spatiotemporal crystal is proposed and analyzed. The parametric oscillation is initiated by the energy and momentum conversion of an incident wave and the subsequent amplification by parametric gain within the momentum band gap. The oscillation process dominates over frequency mixing interactions above a transition threshold determined by the balance between gain and loss. Furthermore, the asymmetric formation of momentum band gaps can be realized by spatial phase control of temporal modulation, which leads to the directional radiation of oscillations at distinct frequencies. The proposed structure would enable simultaneous engineering of energy and momentum band gaps and provide a guideline to the implementation of advanced dispersion-engineered parametric oscillators.

Inorganic Lead-free Cesium Copper Chlorine Nanocrystal for Highly Efficient and Stable Warm White Light-emitting Diodes

Shuangyi Zhao, wensi cai, Huaxin Wang, and Zhigang Zang

DOI: 10.1364/PRJ.409398 Received 03 Sep 2020; Accepted 18 Nov 2020; Posted 18 Nov 2020  View: PDF

Abstract: Inorganic cesium lead halide (CsPbX₃, X = Cl, Br, I) nanocrystals (NCs) attract extensive attentions because of their excellent optoelectronic performance. However, the classic CsPbX₃ NCs suffer from the toxicity and instability, which impede their further applications in commercial fields. Here, the inorganic lead-free cesium copper chlorine nanocrystals are synthesized by a facile hot-injection method. The blue-emission 3D CsCu₃Cl₃ and green-emission 0D Cs₃Cu₂Cl₅ NCs are prepared at 70 and 120 °C, respectively, suggesting that the reaction temperature may account for the final components. Owing to the self-trapped exciton effect, the unique optical properties, such as high photoluminescence quantum yield (PLQY), broadband emission, large Stokes shift, and long PL decay time, are demonstrated for both cesium copper chlorine nanocrystals. Moreover, highly efficient and stable warm white light-emitting diodes are fabricated with CsCu₂Cl₃ and Cs₃Cu₂Cl₅ NCs. The study highlights the promising potential for lead-free cesium copper chlorine nanocrystals in nontoxic solid-state lighting applications.

A Smart Ring Resonator-based Sensor for Multicomponent Chemical Analysis via Machine Learning

ZHENYU LI, Hui Zhang, Binh Nguyen, Shaobo Luo, Patricia Yang Liu, Jun Zou, Yuzhi Shi, Hong Cai, Zhenchuan Yang, yufeng jin, yilong hao, Yi Zhang, and Ai-Qun LIU

DOI: 10.1364/PRJ.411825 Received 06 Oct 2020; Accepted 18 Nov 2020; Posted 20 Nov 2020  View: PDF

Abstract: We demonstrate a smart sensor for label-free multicomponent chemical analysis using a single label-free ring resonator to acquire the entire resonant spectrum of the mixture and a neural network model to predict the composition for multicomponent analysis. The smart sensor shows a high prediction accuracy with a low root mean squared error (RMSE) ranging only from 0.13 to 2.28 mg/mL. The predicted concentrations of each component in the testing dataset almost all fall within the 95% prediction bands. With its simple label-free detection strategy and high accuracy, the smart sensor promises great potential for multicomponent analysis applications in many fields.

Time-resolved second-order interference of true thermal light from warm atomic ensemble in two independent unbalanced interferometers

Han Seb Moon, Jiho Park, and Heonoh Kim

DOI: 10.1364/PRJ.402574 Received 13 Jul 2020; Accepted 15 Nov 2020; Posted 18 Nov 2020  View: PDF

Abstract: We report the demonstration of a second-order interference experiment by use of thermal light emitted from a warm atomic ensemble in two spatially separated unbalanced Michelson interferometers (UMIs). This novel multipath correlation interference with thermal light has been theoretically proposed by Tamma. In our experiment, the bright thermal light used for second-order interference are superradiantly emitted via collective two-photon coherence in Doppler-broadened cascade-type 87Rb atoms. Owing to the long coherence time of the thermal light from the atomic ensemble, we observe its second-order interference in the two independent UMIs by means of time-resolved coincidence detection. Interestingly, the temporal waveforms of the interfering thermal light in the two spatially separated UMIs exhibit similarities with the temporal two-photon waveforms of time–energy entangled photon pairs in Franson interferometry. Our results can contribute toward a better understanding of the relation between first- and second-order interferences that are at the heart of photonics-based quantum information science.

Digital Quantum Simulation of Floquet TopologicalPhases with a Solid-State Quantum Simulator

Bing Chen, Shuo Li, Xianfei Hou, Feifei Zhou, Peng Qian, Feng Mei, Suotang Jia, Nanyang Xu, and Heng Shen

DOI: 10.1364/PRJ.404163 Received 30 Jul 2020; Accepted 15 Nov 2020; Posted 18 Nov 2020  View: PDF

Abstract: Quantum simulator with the ability to harness the dynamics of complex quantum systems has emerged as a promising platform for probing exotic topological phases. Since the flexibility offered by various controllable quantum systems has enabled to gain insight into quantum simulation of such complicated problems, analog quantum simulator has recently shown its feasibility to tackle problems of exploring topological phases. However, digital quantum simulation and detection of topological phases still remainelusive. Here, we develop and experimentally realize the digital quantum simulation of topological phase with a solid-state quantum simulator at room temperature. Distinct from previous works dealing with static topological phases, the topological phases emulated here are Floquet topological phases. Furthermore, we also illustrate the procedure of digitally simulating a quantum quench and observing the nonequilibrium dynamics of Floquet topological phases. By means of quantum quench, the 0-and π-energy topological invariants are unambiguously detected through measuring time-averaged spin polarizations. Our experiment opens up a new avenue to digitally simulate and detect Floquet topologicalphases with fast-developed programmable quantum simulators.

Plasmonic evolution maps for planar metamaterials

Liyong Jiang, Jianli Jiang, zebin zhu, Guanghui Yuan, Ming Kang, and Shen Zexiang

DOI: 10.1364/PRJ.404355 Received 03 Aug 2020; Accepted 15 Nov 2020; Posted 18 Nov 2020  View: PDF

Abstract: Understanding the mode’s origin in planar metamaterials is fundamental for the related applications in nanophotonics and plasmonics. For complex planar metamaterials, conventional analysis that directly obtains the final charge/current distribution of a mode usually has difficulty in understanding the mode’s origin. In this paper, we propose a mode evolution method with a core analysis tool, i.e., plasmonic evolution maps (PEMs), to describe the mode evolution in several complementary planar metamaterials with designed plasmonic atoms/molecules. The PEMs could not only clearly explain a mode’s origin, but also reveal the role of a structure’s symmetry in the mode formation process. The mode evolution method with PEMs can work as a simple, efficient, and universal approach for the mode analysis in different kinds of planar metamaterials.

Photonic two-particle quantum walks in Su-Schrieffer-Heeger lattices

Alexander Szameit, Friederike Klauck, and Matthias Heinrich

DOI: 10.1364/PRJ.409005 Received 01 Sep 2020; Accepted 14 Nov 2020; Posted 18 Nov 2020  View: PDF

Abstract: We report on the experimental demonstration of two-photon quantum walks at the edges of a photonic SSH lattice and compare them to those observed when launching photons at the edge of a homogeneous lattice. Whereas at the topological edge, one of the photons primarily remains close to the edge, both photons penetrate freely from the trivial edge into the bulk. This behavior manifests also in the average inter-particle distance, which is significantly larger at the topological edge. Hence, for a given propagation length, the entangled two-photon state launched at the topological edge extends over a wider domain of the lattice.

Modulation format identification in fiber communications using a single dynamical node based artificial neural network

Qiang Cai, Ya Guo, Pu Li, Adonis Bogris, K. Alan Shore, and Yuncai Wang

DOI: 10.1364/PRJ.409114 Received 09 Sep 2020; Accepted 13 Nov 2020; Posted 18 Nov 2020  View: PDF

Abstract: We present a simple approach based on a photonic reservoir computing (P-RC) for modulation format identification (MFI) in optical fiber communications. Here an optically injected semiconductor laser with self-delay feedback is trained with the representative features from the asynchronous amplitude histograms of modulation signals. Numerical simulations conducted for three widely-used modulation formats (OOK, DQPSK and QAM) for various transmission situations demonstrate that this technique can efficiently identify all those modulation formats with an accuracy of > 95% after optimizing the control parameters of the P-RC layer such as the injection strength, feedback strength, bias current and frequency detuning. The proposed technique utilizes very simple devices and thus offers a resource-efficient alternative approach to MFI.

Sub-diffraction imaging with anomalous saturated excitation

Bo Du, Xiangdong Chen, Zehao Wang, Shao-Chun Zhang, Enhui Wang, Guang-can Guo, and Fang-Wen Sun

DOI: 10.1364/PRJ.410373 Received 17 Sep 2020; Accepted 10 Nov 2020; Posted 12 Nov 2020  View: PDF

Abstract: The nonlinear fluorescence emission has been widely applied for the high spatial resolution optical imaging. Here, we studied the fluorescence anomalous saturating effect of the nitrogen vacancy defect in diamond. The fluorescence reduction was observed with high power laser excitation. It increased the nonlinearity of the fluorescence emission, and changed the spatial frequency distribution of the fluorescence image. We used a differential excitation protocol to extract the high spatial frequency information. By modulating the excitation laser's power, the spatial resolution of imaging was improved approximate 1.6 times in comparison with the confocal microscopy. Due to the simplicity of the experimental setup and data processing, we expect this method can be used for improving the spatial resolution of sensing and biological labeling with the defects in solids.

Dual-band perfect absorber for mid-infrared photodetector based on dielectric metal metasurface

Zhao Chen, Yudong Weng, Junku Liu, Nan Guo, Yaolun Yu, and lin xiao

DOI: 10.1364/PRJ.410554 Received 21 Sep 2020; Accepted 10 Nov 2020; Posted 12 Nov 2020  View: PDF

Abstract: Mid-infrared thermal detectors have very important applications in the aerospace and military fields. However, due to the low heat transfer efficiency and slow response time, its application has been greatly restricted. Here, we theoretically demonstrate a dual-band perfect absorber for mid-infrared detector based on dielectric metal metasurface and the optical and thermal properties are analyzed in detail. Simulation results show that the two narrow absorption peaks, corresponding to the absorption value of 97.5% at λ=6.142 μm with λFWHM≈ 40 nm and 99.7% at λ=7.795 μm with λFWHM≈ 80 nm respectively, are achieved and their different dependences on the structural parameters have been studied. A thermal detector at room temperature with total response time within 1.3 ms for dual-band and 0.4 ms for single-band is realized when the incident light flux is 1.0 W/cm2 for an average temperature increase of ∆T≈1.0 K. Our study offers a promising approach for designing narrow band mid-infrared perfect absorber and high-performance photodetector in nano-integrated photonics.

Elucidating Photoluminescence-Enhancement Mechanism in a Push-Pull Conjugated Polymer Induced by Hot-Electron Injection from Gold Nanoparticles

Dongki Lee, Se Gyo Han, Jungho Mun, Kihyuk Yang, Sung Hyuk Kim, Junsuk Rho, Kilwon Cho, Dongyeop X. Oh, and Mun Seok Jeong

DOI: 10.1364/PRJ.409762 Received 09 Sep 2020; Accepted 09 Nov 2020; Posted 12 Nov 2020  View: PDF

Abstract: Understanding the photophysical interactions between the components in organic-inorganic nanocomposites is a key factor for their efficient application in optoelectronic devices. In particular, the photophysical study of nanocomposites based on organic conjugated polymers is rare. We investigated the effect of surface plasmon resonance (SPR) of gold nanoparticles (Au NPs) on the photoluminescence (PL) property of a push-pull conjugated polymer (PBDB-T). We prepared the hybrid system by incorporating poly(3-hexylthiophene)-stabilized Au NPs into PBDB-T. The enhanced and blue-shifted PL was observed in the hybrid system compared to PL in a neat PBDB-T system, indicating that the P3HT chains attached to the Au NPs suppressed charge-transfer from PBDB-T to the Au NPs and relayed the hot electrons to PBDB-T (the band-filling effect). This photophysical phenomenon limited the auto dissociation of PBDB-T excitons. Thus, the radiative recombination of the excitons more occurred in our hybrid system than in the neat system.

On-chip reconfigurable mode converter based on cross-connected subwavelength Y-junctions

Minming Zhang, Longhui lu, Deming Liu, and Max Yan

DOI: 10.1364/PRJ.402940 Received 15 Jul 2020; Accepted 06 Nov 2020; Posted 06 Nov 2020  View: PDF

Abstract: A novel power-efficient reconfigurable mode converter is proposed and experimentally demonstrated based on cross-connected symmetric Y-junctions assisted by thermo-optic phase shifters on a silicon-on-insulator platform. Instead of using conventional Y-junction, subwavelength symmetric Y-junctions are utilized to enhance the mode splitting ability. The reconfigurable functionality can be realized by controlling the induced phase differences. Benefited from the cross-connected scheme, the number of heating electrodes can be effectively reduced, while the performance of the device is maintained. With only one-step etching, our fabricated device shows the average excess losses and crosstalks are less than 2.45 and –16.6 dB, respectively, measured with conversions between two arbitrary compositions of the first four TE modes over an observable 60 nm bandwidth. The converter is switchable, CMOS-compatible and could be extended for more modes; hence it can be potentially deployed for advanced and flexible mode multiplexing optical networks-on-chip.

Superior Single-Mode Lasing in Self-Assembly CsPbX3 Microcavity over an Ultrawide Pumping Wavelength Range

Guo-En Weng, Jiyu Yan, Shengjie Chen, Chunhu Zhao, Hanbing Zhang, Jiao Tian, Yuejun liu, Xiaobo Hu, Jiahua Tao, Shaoqiang Chen, Ziqiang Zhu, Hidefumi Akiyama, and Junhao Chu

DOI: 10.1364/PRJ.409884 Received 10 Sep 2020; Accepted 06 Nov 2020; Posted 06 Nov 2020  View: PDF

Abstract: All-inorganic perovskite micro/nanolasers are emerging as a class of miniaturized coherent photonic sources for many potential applications, such as optical communication, computing, and imaging, owing to their ultracompact sizes, highly localized coherent output, and broadband wavelength tunability. However, to achieve single-mode laser emission in the microscale perovskite cavity is still challenging. Herein, we report unprecedented single-mode laser operations at room temperature in self-assembly CsPbX3 microcavities over an ultrawide pumping wavelength range of 400- 00 nm, covering one- to five-photon absorption processes. The superior frequency down- and up-conversion single-mode lasing manifests high multiphoton absorption efficiency and excellent optical gain from the electron–hole plasma state in the perovskite microcavities. Through direct compositional modulation, the wavelength of a single-mode CsPbX3 microlaser can be continuously tuned from blue-violet to green (427-543 nm). The laser emission remains stable and robust after long-term high-intensity excitation for over 12 h (up to 4.3 × 107 excitation cycles) in the ambient atmosphere. Moreover, the pump-wavelength dependence of the threshold, as well as the detailed lasing dynamics such as gain-switching and electron–hole plasma mechanism, are systematically investigated to shed insight into the more fundamental issues of the lasing processes in CsPbX3 perovskite microcavity.

Photonic Smart Bandage for Wound Healing Assessment

Arnaldo Leal Junior, Jingjing Guo, Rui Min, Antonio Fernandes, Anselmo Frizera-Neto, and Carlos Marques

DOI: 10.1364/PRJ.410168 Received 14 Sep 2020; Accepted 03 Nov 2020; Posted 03 Nov 2020  View: PDF

Abstract: Chronic wounds affect around 2% of the world population with an annual multi-billion dollars cost to the healthcare system. This background pushes the development of new therapies and procedures for wound healing and its assessment. Among them, the potential of Hydrogen (pH) assessment is an important indicator of the wound healing stage and condition. This paper presents the development of the first optical fibre-embedded smart wound dressing for pH assessment. An intrinsically pH sensitive optical fibre is fabricated using a polydimethylsiloxane (PDMS) precursor doped with Rhodamine B dye. Raman and Fourier Transform Infrared (FTIR) spectroscopies are performed in order to verify the presence of Rhodamine B and PDMS in the fibre samples. Then, the fibre is embedded in gauze fabric and hydrocolloid wound dressing. In addition, such low Young’s modulus of PDMS fibre enables its use as a highly sensitive pressure sensor, where the results show that the fibre-embedded bandage can measure pressures as low as 0.1 kPa with a high linearity in the range of 0 to 0.3 kPa. The smart bandage is subjected to different pH, which resulted in a wavelength shift of 0.67 nm/pH when the absorption peak at 515 nm is analysed. Furthermore, pH increase lead to linear decrease of the transmitted optical power (R2 of 0.998), with rise and fall times below 20 s and 30 s, respectively. Therefore, the proposed optical fibre-embedded smart bandage enables the simultaneous assessment of pressure and pH on the wound region.

Long Distance Ranging with High Precision using Soliton Microcomb

Jindong Wang, zhizhou lu, Weiqiang Wang, FuMin Zhang, JIAWEI chen, yang wang, JIHUI ZHENG, Sai Chu, Wei Zhao, Brent Little, XingHua Qu, and Wenfu Zhang

DOI: 10.1364/PRJ.408923 Received 08 Sep 2020; Accepted 28 Oct 2020; Posted 02 Nov 2020  View: PDF

Abstract: Laser-based light detection and ranging (LIDAR) plays a significant role in both scientific and industrial areas. However, it is difficult for existing LIDARs to achieve high speed, high precision and long distance simultaneously. Here, we demonstrate a high-performance LIDAR based on chip-scaled soliton microcomb (SMC) that can realize all three specialties simultaneously. Aided by the excellent properties of ultrahigh repetition rate and smooth envelope of SMC, traditional optical frequency comb (OFC) based dispersive interferometry (DPI) is heavily improved that the measuring dead-zone induced by the mismatch between the repetition rate of OFC and resolution of optical spectrum analyzer is totally eliminated. Combined with an auxiliary dual-frequency phase-modulated laser rangefinder, the none-dead-zone measurable range ambiguity is extended up to 1500 m. The proposed SMC LIDAR is experimentally implemented in both indoor and outdoor environment. In the outdoor baseline field, real-time, high-speed (up to 35 kHz) measurement of a long distance of ~1179 m is achieved with a minimum Allan deviation of 5.6 μm at averaging time of 0.2 ms (27 nm at averaging time of 1.8 s after high-pass filtering). The present SMC LIDAR approaches a compact, fast, high-precision, and none-dead-zone long distance ranging system, aiming to the emerging applications of frontier basic scientific researches and advances industrial manufacturing.

Bias-drift-free Mach-Zehnder modulators based on heterogeneous silicon and lithium niobate platform

Shihao Sun, mingbo he, Mengyue Xu, Shengqian Gao, Ziyan Chen, xian zhang, Ziliang Ruan, Xiong Wu, Lidan Zhou, Lin Liu, Chao Lu, Changjian Guo, Liu Liu, Siyuan Yu, and Xinlun Cai

DOI: 10.1364/PRJ.403167 Received 20 Jul 2020; Accepted 22 Oct 2020; Posted 23 Oct 2020  View: PDF

Abstract: Optical modulators have been and will continue to be essential devices for energy- and cost-efficient optical communication networks. Heterogeneous silicon and lithium niobate modulators have demonstrated promising performances of low optical loss, low drive voltage, and large modulation bandwidth. However, DC bias drift is a major drawback of optical modulators using Lithium Niobate as the active electrooptic material. Here, we demonstrate high-speed and bias-drift-free Mach-Zehnder modulators based on the heterogeneous silicon and lithium niobate platform. The devices combine stable thermo-optic DC biases in silicon and ultra-fast electro-optic modulation in lithium niobite, and exhibit a low insertion loss of 1.8 dB, a low half-wave voltage of 3 V, electro-optic modulation bandwidth of at least 70 GHz and modulation data rates up to 128 Gbit/s.

All-optical motion control of metal nanoparticles powered by propulsion forces tailored in 3D trajectories

Jose Rodrigo, Mercedes Angulo, and Tatiana Alieva

DOI: 10.1364/PRJ.408680 Received 28 Aug 2020; Accepted 22 Oct 2020; Posted 23 Oct 2020  View: PDF

Abstract: Increasing interest has been drawn to optical manipulation of metal (plasmonic) nanoparticles due to their unique response on electromagnetic radiation prompting numerous applications in nanofabrication, photonics, sensing, etc. The familiar point-like laser tweezers rely on the exclusive use of optical confinement forces that allow stable trapping of a single metal nanoparticle in 3D. All-optical manipulation enabling motion control of single and multiple metal nanoparticles is one of the major challenges to be overcome. This article reports and provides guidance to mastering a sophisticated all-optical manipulation technique harnessing confinement and propulsion forces enabling nanoparticle motion control along 3D trajectories. As an example it is experimentally demonstrated, for the first time, programmable transport of gold and silver nano-spheres with a radius of 50~nm and 30~nm, respectively, along 3D trajectories tailored on demand. It has been achieved by an independent design of both types of optical forces in a single-beam laser trap in the form of reconfigurable 3D curve. The controlled motion of multiple nanoparticles, far away from chamber walls, allows studying induced electrodynamic interactions between them, such as plasmonic coupling, observed in the presented experiments. The independent control of optical confinement and propulsion forces provides enhanced flexibility to manipulate matter with light paving the way to new applications involving the formation, sorting, delivery, and assembling of nanostructures.

First experimental demonstration of coherent beam combining of more than 100 fiber lasers

Hongxiang Chang, Qi Chang, Jiachao Xi, Tianyue Hou, Rongtao Su, Pengfei Ma, Jian Wu, Can Li, Man Jiang, Yanxing Ma, and Pu Zhou

DOI: 10.1364/PRJ.409788 Received 09 Sep 2020; Accepted 21 Oct 2020; Posted 23 Oct 2020  View: PDF

Abstract: Coherent beam combining (CBC) of 107 fiber lasers has been demonstrated for the first time. When the system was in closed loop, the pattern in far-field was stable and the fringe contrast was >96%. The impact of dynamic tilt error, piston error and power inconsistency were theoretically analyzed. Meanwhile, the distribution law of dynamic tilt error was estimated and the correlation of the tilt dithering of different axis was analyzed statistically. It was found that the tilt dithering of the direction perpendicular to the platform was medium correlative between array elements with the Pearson correlation coefficient was ~0.43. And the phase residue error in the closed loop was ~λ/22 evaluated by root-mean-square error of signal generated from photoelectric detector.

Nonlinear silicon photonics on CMOS compatible tellurium oxide

Neetesh Singh, Hamidu M. Mbonde, Henry Frankis, Erich Ippen, Jonathan Bradley, and Franz Kaertner

DOI: 10.1364/PRJ.400057 Received 23 Jun 2020; Accepted 18 Oct 2020; Posted 19 Oct 2020  View: PDF

Abstract: Silicon photonics is coming of age; however, it is still lacking a monolithic platform for optical sources and nonlinear functionalities prompting heterogeneous integration of different materials tailored to different applications. Here we demonstrate tellurium oxide as a potential monolithic complementary metal oxide semiconductor (CMOS) silicon photonics platform for nonlinear functionalities, which is already becoming an established platform for sources and amplifiers. We show broad band supercontinuum generation covering the entire telecom window and show for the first time third harmonic generation in its integrated embodiment. Together with the now available lasers and amplifiers on integrated TeO2 this work paves the way for a monolithic TeO2 based nonlinear silicon photonics platform.

Generalizing the Gerchberg-Saxton algorithm for retrieving optical transmission matrices of disordered media

Guoqiang Huang, Daixuan Wu, Jiawei Luo, Fan Li, Yuecheng Shen, Zhaohui Li, and Liang Lu

DOI: 10.1364/PRJ.406010 Received 20 Aug 2020; Accepted 17 Oct 2020; Posted 05 Nov 2020  View: PDF

Abstract: The Gerchberg-Saxton (GS) algorithm, which retrieves phase information from the measured intensities on two related planes (the source plane and the target plane), has been widely adopted in a variety of applications when holographic methods are challenging to be implemented. In this work, we showed that the GS algorithm can also be generalized to retrieve the unknown propagating function that connects these two planes. As a proof-of-concept, we employed the generalized GS (GGS) algorithm to retrieve the optical transmission matrix (TM) of a disordered medium through the measured intensity distributions on the target plane. Numerical studies indicate that the GGS can retrieve the optical TM efficiently and accurately. Using the same training data set, the computational time cost by the GGS is orders of magnitude less than that consumed by other non-holographic methods reported in the literature. Besides numerical investigations, we also experimentally demonstrated retrieving the optical TMs of diffusers and a 1-meter long multimode fiber using the GGS. The accuracy of the retrieved TM was evaluated by synthesizing high-quality single foci and multiple foci on the target plane through these disordered media. These results indicate that the GGS is well suited to handle a large TM, showing great promise in a variety of applications in optics.

High-performance Fiber-Integrated Multi-functional Graphene-Optoelectronic Device with Photoelectric Detection and Optic-Phase Modulation

Linqing Zhuo, Pengpeng Fan, Shuang Zhang, Yuansong Zhan, Yanmei Lin, Yu Zhang, Dongquan Li, Zhen Che, Wenguo Zhu, Harry Zheng, Jieyuan Tang, Jun Zhang, Yongchun Zhong, Wenxiao Fang, Guoguang lu, JianHui Yu, and zhe chen

DOI: 10.1364/PRJ.402108 Received 07 Jul 2020; Accepted 05 Oct 2020; Posted 13 Oct 2020  View: PDF

Abstract: In graphene-based optoelectronic devices, the ultra-weak interaction between a light and a monolayer graphene leads to low optical absorption and low responsivity for the photodetectors and relative high half-wave voltage for the phase modulator. Here, an integration of the monolayer graphene onto the side-polished optical fiber is demonstrated capable of providing a cost-effective strategy to enhance the light-graphene interaction, allowing us to obtain a high-efficient optical absorption in graphene and achieve multi-functions: photodetection and optical phase modulation. As a photodetector, the device has an ultra-high responsivity (1.5×10⁷ A/W) and a high external quantum efficiency (>1.2×10⁹ %). Additionally, the polybutadiene (PB)/polymethyl methacrylate (PMMA) film on the graphene can render the device an optical phase modulator through the large thermo-optic effect of the PMMA. As a phase modulator, the device has a relative low half-wave voltage of 3 V with a 16 dB extinction ratio in Mach-Zender interferometer configuration.

Metasurface-based subtractive color filter fabricated on a 12-inch glass wafer using CMOS platform

Zhengji XU, Nanxi Li, yuan dong, Yuan Hsing Fu, Ting Hu, Qize Zhong, Yanyan Zhou, Dongdong Li, Shiyang Zhu, and Navab Singh

DOI: 10.1364/PRJ.404124 Received 31 Jul 2020; Accepted 27 Sep 2020; Posted 28 Sep 2020  View: PDF

Abstract: Optical color filters are widely applied in many areas including display, imaging, sensing, holography, energy harvest, and measurement. The traditional dye-based color filters have drawbacks such as environmental hazards and instability under high temperature and ultra-violet radiation. With the advance of the nanotechnology, the structural color filters, which are based on the interaction of light with designed nanostructures, are able to overcome the short comings. Also, it is possible to fabricate structural color filters using the standard complementary metal-oxide-semiconductor (CMOS) fabrication facilities with low cost and high volume. In this work, metasurface-based subtractive color filters are demonstrated on 12-inch glass wafers using CMOS-compatible fabrication process. Three different heights of embedded silicon nanopillars (110, 170 and 0 nm) are found to support magnetic dipole resonances. With pillar height and pitch variation, subtractive color filters (SCFs) with different displayed colors are achieved. Based on the resonance wavelength, the displayed color of the metasurface is verified within the red-yellow-blue (RYB) color wheel. The simulation and measurement results are compared and discussed. The work provides an alternative design for high efficiency color filters on CMOS-compatible platform, and paves the way towards mass-producible large-area metasurface.

Quantum dot mode-locked frequency comb with ultra-stable 25.5 GHz spacing between 20 °C and 120 °C

Siming Chen, Shujie Pan, Jianou Huang, Zichuan Zhou, Zhixin Liu, Lalitha Ponnampalam, Zizhuo Liu, Mingchu Tang, Zizheng Cao, Kenichi Nishi, KEIZO TAKEMASA, Mitsuru Sugawara, Richard Penty, Ian White, Alwyn Seeds, Huiyun Liu, and Mu-Chieh Lo

DOI: 10.1364/PRJ.399957 Received 10 Jun 2020; Accepted 14 Sep 2020; Posted 18 Sep 2020  View: PDF

Abstract: Semiconductor mode-locked lasers (MLLs) are promising frequency comb sources for dense wavelength-division-multiplex (DWDM) data communications. Practical data communication requires a frequency-stable comb source in a temperature-varying environment and a minimum tone spacing of 25 GHz to support high-speed DWDM transmissions. However, to date, there have been no demonstrations of comb sources that simultaneously offer a high repetition rate and stable mode spacing over an ultrawide temperature range. Here, we report a frequency comb source based on a quantum dot (QD) MLL that generates a frequency comb with stable mode spacing over an ultra-broad temperature range of 20 °C - 120 °C. The two-section passively mode-locked InAs QD MLL comb source produces an ultra-stable fundamental repetition rate of 25.5 GHz (corresponding to a 25.5 GHz spacing between adjacent tones in the frequency domain) with a variation of 0.07 GHz in the tone spacing over the tested temperature range. By keeping the saturable absorber (SA) reversely biased at -2 V, stable mode-locking over the whole temperature range can be achieved by tuning the current of the gain section only, providing easy control of the device. At an elevated temperature of 60 °C, the device shows a 6-dB comb bandwidth of 8.38 nm and 56 tones with > 36 dB optical signal-to-noise ratio (OSNR). The corresponding relative intensity noise (RIN), averaged between 0.5 GHz and 10 GHz, is −148 dBc/Hz. Our results show the viability of the InAs QD MLLs as ultra-stable, uncooled frequency comb sources for low-cost, large-bandwidth and low energy consumption optical data communications.

Advances in on-chip photonic devices based on lithium niobate on insulator

Jintian Lin, Fang Bo, Ya Cheng, and Jingjun Xu

DOI: 10.1364/PRJ.395305 Received 16 Apr 2020; Accepted 01 Sep 2020; Posted 02 Sep 2020  View: PDF

Abstract: Crystalline lithium niobate (LN) is an important optical material for its broad transmission window spanning from ultraviolet to mid-infrared as well as the large nonlinear and electro-optic coefficients. Furthermore, the recent development and commercialization of lithium niobate on insulator (LNOI) technology has opened a venue to the realization of integrated on-chip photonic devices of unprecedented performances in terms of propagation loss, optical nonlinearity and electro-optic tunability. In this review, we begin with a brief introduction on the history and current status of LNOI photonics. Then, we discuss the fabrication techniques of LNOI-based photonic structures and devices. As a matter of fact, the recent revolution in the LN photonic industry is sparked and still being powered by the innovations of nanofabrication technology of LNOI, enabling production of the building block structures such as optical microresonators and waveguides of unprecedented optical qualities. In the following sections, we present a variety of on-chip LNOI devices which are categorized into nonlinear photonic devices, electro-optic tunable devices, and photonic integrated circuits. At last, some conclusions and the future perspective will be provided.

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