Contents
2 Issue (s), 37 Article (s)
Vol.10, Iss.6—Jun.1, 2022 • pp: 1325-1471 Spec. pp: A82-A96
Vol.10, Iss.5—May.1, 2022 • pp: 1146-1324 Spec. pp: A66-A81
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Research ArticlesVol.10, Iss.6-Jun..1,2022
Fiber Optics and Optical Communications
Multiphoton ionization of standard optical fibersM. Ferraro, F. Mangini, Y. Sun, M. Zitelli, A. Niang, M. C. Crocco, V. Formoso, R. G. Agostino, R. Barberi, A. De Luca, A. Tonello, V. Couderc, S. A. Babin, and S. Wabnitz
Atoms ionization by the simultaneous absorption of multiple photons has found applications in fiber optics, where it leads to unique nonlinear phenomena. To date, studies of the ionization regime have been limited to gas-filled hollow-core fibers. Here, we investigate multiphoton ionization of standard optical fibers, where intense laser pulses ionize the atoms constituting the fiber structure itself, instead of that of the filling gas. We characterize material modifications produced by optical breakdown. Their formation affects laser beam dynamics over hours long temporal scales. The damage features are studied by means of optical microscopy and X-ray microtomography. In the framework of glass photonics, our results pave the way for a novel glass waveguide micromachining technique.Atoms ionization by the simultaneous absorption of multiple photons has found applications in fiber optics, where it leads to unique nonlinear phenomena. To date, studies of the ionization regime have been limited to gas-filled hollow-core fibers. Here, we investigate multiphoton ionization of standard optical fibers, where intense laser pulses ionize the atoms constituting the fiber structure itself, instead of that of the filling gas. We characterize material modifications produced by optical breakdown. Their formation affects laser beam dynamics over hours long temporal scales. The damage features are studied by means of optical microscopy and X-ray microtomography. In the framework of glass photonics, our results pave the way for a novel glass waveguide micromachining technique.
Photonics Research
- Publication Date: May. 12, 2022
- Vol.10 Issue, 6 06001394 (2022)
Instrumentation and Measurements
Coherent-detection-based distributed acoustic impedance sensing enabled by a chirped fiber Bragg grating arrayZhou Zheng, Zhengying Li, Xuelei Fu, and Xin Gui
Distributed optical fiber sensing exploring forward stimulated Brillouin scattering (FSBS) has received wide attention, as it indicates a new sensing method to measure the liquid property surrounding an optical fiber. In the existing techniques, backward stimulated Brillouin scattering is adopted for detection of the sensing signal, which requires time-consuming signal acquisition and post-processing. In this work, an approach that distributedly measures FSBS spectra is proposed and demonstrated based on coherent detection. While an excitation pulse with single-frequency amplitude modulation is used to induce a guided acoustic mode in the fiber, a following pulse is adopted to probe the induced phase modulation. Using a chirped fiber Bragg grating array, an enhanced-backward-propagating sensing signal is generated from the probe pulse. Heterodyne coherent-detection-based phase demodulation is then realized by mixing the sensing signal with a local oscillator. The FSBS spectra can then be reconstructed from the beat signals with only one round of frequency sweeping. With significantly accelerated signal acquisition and simplified post-processing, the proposed distributed acoustic sensing system has achieved spatial resolution of 5 m over a 500-m sensing range.Distributed optical fiber sensing exploring forward stimulated Brillouin scattering (FSBS) has received wide attention, as it indicates a new sensing method to measure the liquid property surrounding an optical fiber. In the existing techniques, backward stimulated Brillouin scattering is adopted for detection of the sensing signal, which requires time-consuming signal acquisition and post-processing. In this work, an approach that distributedly measures FSBS spectra is proposed and demonstrated based on coherent detection. While an excitation pulse with single-frequency amplitude modulation is used to induce a guided acoustic mode in the fiber, a following pulse is adopted to probe the induced phase modulation. Using a chirped fiber Bragg grating array, an enhanced-backward-propagating sensing signal is generated from the probe pulse. Heterodyne coherent-detection-based phase demodulation is then realized by mixing the sensing signal with a local oscillator. The FSBS spectra can then be reconstructed from the beat signals with only one round of frequency sweeping. With significantly accelerated signal acquisition and simplified post-processing, the proposed distributed acoustic sensing system has achieved spatial resolution of 5 m over a 500-m sensing range.
Photonics Research
- Publication Date: May. 06, 2022
- Vol.10 Issue, 6 06001325 (2022)
Instrumentation and Measurements
Single-shot terahertz polarization detection based on terahertz time-domain spectroscopyQinggang Lin, Xinming Yuan, Xuanke Zeng, Yatao Yang, Yi Cai, Xiaowei Lu, Maijie Zheng, Congying Wang, Wenhua Cao, and Shixiang Xu
This paper presents a novel design for single-shot terahertz polarization detection based on terahertz time-domain spectroscopy (THz-TDS). Its validity has been confirmed by comparing its detection results with those of the THz common-path spectral interferometer through two separate measurements for the orthogonal components. Our results also show that its detection signal-to-noise ratios (SNRs) are obviously superior to those of the 45° optical bias THz-TDS by electro-optical sampling due to its operation on common-path spectral interference rather than the polarization-sensitive intensity modulation. The setup works without need of any optical scan, which does not only save time, but also efficiently avoids the disturbances from the fluctuations of the system and environment. Its single-shot mode allows it to work well for the applications with poor or no repeatability.This paper presents a novel design for single-shot terahertz polarization detection based on terahertz time-domain spectroscopy (THz-TDS). Its validity has been confirmed by comparing its detection results with those of the THz common-path spectral interferometer through two separate measurements for the orthogonal components. Our results also show that its detection signal-to-noise ratios (SNRs) are obviously superior to those of the 45° optical bias THz-TDS by electro-optical sampling due to its operation on common-path spectral interference rather than the polarization-sensitive intensity modulation. The setup works without need of any optical scan, which does not only save time, but also efficiently avoids the disturbances from the fluctuations of the system and environment. Its single-shot mode allows it to work well for the applications with poor or no repeatability.
Photonics Research
- Publication Date: May. 12, 2022
- Vol.10 Issue, 6 06001374 (2022)
Integrated Optics
Heterogeneous integrated phase modulator based on two-dimensional layered materialsHao Chen, Zexing Zhao, Ziming Zhang, Guoqing Wang, Jiatong Li, Zhenyuan Shang, Mengyu Zhang, Kai Guo, Junbo Yang, and Peiguang Yan
Silicon nitride, with ultralow propagation loss and a wide transparency window, offers an exciting platform to explore integrated photonic devices for various emerging applications. It is appealing to combine the intrinsic optical properties of two-dimensional layered materials with high-quality optical waveguides and resonators to achieve functional devices in a single chip. Here we demonstrate a micro-ring resonator-based phase modulator integrated with few-layer
Photonics Research
- Publication Date: May. 16, 2022
- Vol.10 Issue, 6 06001401 (2022)
Medical Optics and Biotechnology
High-axial-resolution optical stimulation of neurons Cheng Jin, Chi Liu, and Lingjie Kong
Two-photon optogenetics has become an indispensable technology in neuroscience, due to its capability in precise and specific manipulation of neural activities. A scanless holographic approach is generally adopted to meet the requirement of stimulating neural ensembles simultaneously. However, the commonly used disk patterns fail in achieving single-neuron resolution, especially in axial dimension, and their inherent speckles decrease stimulation efficiency. Here, we propose a novel speckle-free, beaded-ring pattern for high-axial-resolution optical stimulation of neurons in vivo. Using a dye pool and a fluorescent thin film as samples, we verify that, compared to those with disk patterns, higher axial resolution and better localization ability can be achieved with beaded-ring patterns. Furthermore, we perform two-photon based all-optical physiology with neurons in mouse S1 cortex in vivo, and demonstrate that the axial resolution obtained by beaded-ring patterns can be improved by 24% when stimulating multiple neurons, compared to that of disk patterns. Two-photon optogenetics has become an indispensable technology in neuroscience, due to its capability in precise and specific manipulation of neural activities. A scanless holographic approach is generally adopted to meet the requirement of stimulating neural ensembles simultaneously. However, the commonly used disk patterns fail in achieving single-neuron resolution, especially in axial dimension, and their inherent speckles decrease stimulation efficiency. Here, we propose a novel speckle-free, beaded-ring pattern for high-axial-resolution optical stimulation of neurons in vivo. Using a dye pool and a fluorescent thin film as samples, we verify that, compared to those with disk patterns, higher axial resolution and better localization ability can be achieved with beaded-ring patterns. Furthermore, we perform two-photon based all-optical physiology with neurons in mouse S1 cortex in vivo, and demonstrate that the axial resolution obtained by beaded-ring patterns can be improved by 24% when stimulating multiple neurons, compared to that of disk patterns.
Photonics Research
- Publication Date: May. 12, 2022
- Vol.10 Issue, 6 06001367 (2022)
Nanophotonics and Photonic Crystals
Broadband high-efficiency polymerized liquid crystal metasurfaces with spin-multiplexed functionalities in the visibleXinjian Lu, Xiaoyin Li, Yinghui Guo, Mingbo Pu, Jiangyu Wang, Yaxin Zhang, Xiong Li, Xiaoliang Ma, and Xiangang Luo
Traditional optical components are usually designed for a single functionality and narrow operation band, leading to the limited practical applications. To date, it is still quite challenging to efficiently achieve multifunctional performances within broadband operating bandwidth via a single planar optical element. Here, a broadband high-efficiency polarization-multiplexing method based on a geometric phase polymerized liquid crystal metasurface is proposed to yield the polarization-switchable functionalities in the visible. As proofs of the concept, two broadband high-efficiency polymerized liquid crystal metalenses are designed to obtain the spin-controlled behavior from diffraction-limited focusing to sub-diffraction focusing or focusing vortex beams. The experimental results within a broadband range indicate the stable and excellent optical performance of the planar liquid crystal metalenses. In addition, low-cost polymerized liquid crystal metasurfaces possess unique superiority in large-scale patterning due to the straightforward processing technique rather than the point-by-point nanopatterning method with high cost and low throughput. The high-efficiency liquid crystal metasurfaces also have unrivalled advantages benefiting from the characteristic with low waveguide absorption. The proposed strategy paves the way toward multifunctional and high-integrity optical systems, showing great potential in mobile devices, optical imaging, robotics, chiral materials, and optical interconnections.Traditional optical components are usually designed for a single functionality and narrow operation band, leading to the limited practical applications. To date, it is still quite challenging to efficiently achieve multifunctional performances within broadband operating bandwidth via a single planar optical element. Here, a broadband high-efficiency polarization-multiplexing method based on a geometric phase polymerized liquid crystal metasurface is proposed to yield the polarization-switchable functionalities in the visible. As proofs of the concept, two broadband high-efficiency polymerized liquid crystal metalenses are designed to obtain the spin-controlled behavior from diffraction-limited focusing to sub-diffraction focusing or focusing vortex beams. The experimental results within a broadband range indicate the stable and excellent optical performance of the planar liquid crystal metalenses. In addition, low-cost polymerized liquid crystal metasurfaces possess unique superiority in large-scale patterning due to the straightforward processing technique rather than the point-by-point nanopatterning method with high cost and low throughput. The high-efficiency liquid crystal metasurfaces also have unrivalled advantages benefiting from the characteristic with low waveguide absorption. The proposed strategy paves the way toward multifunctional and high-integrity optical systems, showing great potential in mobile devices, optical imaging, robotics, chiral materials, and optical interconnections.
Photonics Research
- Publication Date: May. 12, 2022
- Vol.10 Issue, 6 06001380 (2022)
Optical and Photonic Materials
3D printing of optical materials by processes based on photopolymerization: materials, technologies, and recent advancesEmma Geisler, Maxime Lecompère, and Olivier Soppera
3D printing technologies have expanded beyond the research laboratories where they were used solely for prototyping and have become widely used in several industries. The production of custom 3D objects has significant potential in optical applications. However, this necessitates extremely specific material properties, such as transparency, homogeneity, birefringence, and surface finish. Currently, the majority of optical objects are manufactured using plastics. Moreover, the 3D printing processes using polymers to produce optical objects have significant advantages, such as limited wastage, short manufacturing time, and easy customization. However, despite extensive efforts, no technology has achieved the production of objects perfectly suited for optical applications. The objective of this review is to summarize recent advances in the field of 3D printing for optics, with an emphasis on specific developments for dedicated applications, and to explore new candidate processes.3D printing technologies have expanded beyond the research laboratories where they were used solely for prototyping and have become widely used in several industries. The production of custom 3D objects has significant potential in optical applications. However, this necessitates extremely specific material properties, such as transparency, homogeneity, birefringence, and surface finish. Currently, the majority of optical objects are manufactured using plastics. Moreover, the 3D printing processes using polymers to produce optical objects have significant advantages, such as limited wastage, short manufacturing time, and easy customization. However, despite extensive efforts, no technology has achieved the production of objects perfectly suited for optical applications. The objective of this review is to summarize recent advances in the field of 3D printing for optics, with an emphasis on specific developments for dedicated applications, and to explore new candidate processes.
Photonics Research
- Publication Date: May. 12, 2022
- Vol.10 Issue, 6 06001344 (2022)
Optical and Photonic Materials
Wideband diffusion metabsorber for perfect scattering field reductionZicheng Song, Pingping Min, Jiaqi Zhu, Lei Yang, and Feng Han Lin
Both absorption and diffuse reflection can effectively suppress microwave backward reflection. However, the challenge of designing wideband absorptive elements with anti-phase reflection hinders the simultaneous working of the two principles. With aid of the wideband characteristic of bilateral complementary structure, we propose a strategy to design wideband absorptive elements with large reflection phase differences. For proof of concept, the proposed elements are arranged in a rectangular grid by optimizing scattering field distribution. The proposed diffusion metabsorber achieves over 20-dB scattering field reduction in the range of 8.5–20.3 GHz with good polarization stability and high angular insensitivity of up to
Photonics Research
- Publication Date: May. 12, 2022
- Vol.10 Issue, 6 06001361 (2022)
Optical and Photonic Materials
Passivation of degradation path enables high performance perovskite nanoplatelet lasers with high operational stabilityGuohui Li, Huihui Pi, Yanfu Wei, Bolin Zhou, Ya Gao, Rong Wen, Yuying Hao, Han Zhang, Beng S. Ong, and Yanxia Cui
Photonics Research
- Publication Date: May. 20, 2022
- Vol.10 Issue, 6 06001440 (2022)
Optical Devices
Evanescent waveguide lab-on-chip for optical biosensing in food quality controlAlessio Buzzin, Rita Asquini, Domenico Caputo, and Giampiero de Cesare
Optical biosensing systems are commonly developed assembling a source, a light–sample interaction area, and a detector as distinct stand-alone elements. We present a compact, inexpensive, and easy-to-use glass chip that monolithically integrates both the interaction and detection elements in a
Photonics Research
- Publication Date: May. 20, 2022
- Vol.10 Issue, 6 06001453 (2022)
Optical Devices
Neural network-based surrogate model for inverse design of metasurfacesGuoqing Jing, Peipei Wang, Haisheng Wu, Jianjun Ren, Zhiqiang Xie, Junmin Liu, Huapeng Ye, Ying Li, Dianyuan Fan, and Shuqing Chen
Metasurfaces composed of spatially arranged ultrathin subwavelength elements are promising photonic devices for manipulating optical wavefronts, with potential applications in holography, metalens, and multiplexing communications. Finding microstructures that meet light modulation requirements is always a challenge in designing metasurfaces, where parameter sweep, gradient-based inverse design, and topology optimization are the most commonly used design methods in which the massive electromagnetic iterations require the design computational cost and are sometimes prohibitive. Herein, we propose a fast inverse design method that combines a physics-based neural network surrogate model (NNSM) with an optimization algorithm. The NNSM, which can generate an accurate electromagnetic response from the geometric topologies of the meta-atoms, is constructed for electromagnetic iterations, and the optimization algorithm is used to search for the on-demand meta-atoms from the phase library established by the NNSM to realize an inverse design. This method addresses two important problems in metasurface design: fast and accurate electromagnetic wave phase prediction and inverse design through a single phase-shift value. As a proof-of-concept, we designed an orbital angular momentum (de)multiplexer based on a phase-type metasurface, and 200 Gbit/s quadrature-phase shift-keying signals were successfully transmitted with a bit error rate approaching
Photonics Research
- Publication Date: May. 20, 2022
- Vol.10 Issue, 6 06001462 (2022)
Optoelectronics
Optically pumped low-threshold microdisk lasers on a GeSn-on-insulator substrate with reduced defect densityYongduck Jung, Daniel Burt, Lin Zhang, Youngmin Kim, Hyo-Jun Joo, Melvina Chen, Simone Assali, Oussama Moutanabbir, Chuan Seng Tan, and Donguk Nam
Despite the recent success of GeSn infrared lasers, the high lasing threshold currently limits their integration into practical applications. While structural defects in epitaxial GeSn layers have been identified as one of the major bottlenecks towards low-threshold GeSn lasers, the effect of defects on the lasing threshold has not been well studied yet. Herein, we experimentally demonstrate that the reduced defect density in a GeSn-on-insulator substrate improves the lasing threshold significantly. We first present a method of obtaining high-quality GeSn-on-insulator layers using low-temperature direct bonding and chemical–mechanical polishing. Low-temperature photoluminescence measurements reveal that the reduced defect density in GeSn-on-insulator leads to enhanced spontaneous emission and a reduced lasing threshold by
Photonics Research
- Publication Date: May. 12, 2022
- Vol.10 Issue, 6 06001332 (2022)
Optoelectronics
High-performance modified uni-traveling carrier photodiode integrated on a thin-film lithium niobate platformXiangwen Guo, Linbo Shao, Lingyan He, Kevin Luke, Jesse Morgan, Keye Sun, Junyi Gao, Ta-Ching Tzu, Yang Shen, Dekang Chen, Bingtian Guo, Fengxin Yu, Qianhuan Yu, Masoud Jafari, Marko Lončar, Mian Zhang, and Andreas Beling
Lithium niobate on insulator (LNOI) has become an intriguing platform for integrated photonics for applications in communications, microwave photonics, and computing. Whereas, integrated devices including modulators, resonators, and lasers with high performance have been recently realized on the LNOI platform, high-speed photodetectors, an essential building block in photonic integrated circuits, have not been demonstrated on LNOI yet. Here, we demonstrate for the first time, heterogeneously integrated modified uni-traveling carrier photodiodes on LNOI with a record-high bandwidth of 80 GHz and a responsivity of 0.6 A/W at a 1550-nm wavelength. The photodiodes are based on an n-down InGaAs/InP epitaxial layer structure that was optimized for high carrier transit time-limited bandwidth. Photodiode integration was achieved using a scalable wafer die bonding approach that is fully compatible with the LNOI platform.Lithium niobate on insulator (LNOI) has become an intriguing platform for integrated photonics for applications in communications, microwave photonics, and computing. Whereas, integrated devices including modulators, resonators, and lasers with high performance have been recently realized on the LNOI platform, high-speed photodetectors, an essential building block in photonic integrated circuits, have not been demonstrated on LNOI yet. Here, we demonstrate for the first time, heterogeneously integrated modified uni-traveling carrier photodiodes on LNOI with a record-high bandwidth of 80 GHz and a responsivity of 0.6 A/W at a 1550-nm wavelength. The photodiodes are based on an n-down InGaAs/InP epitaxial layer structure that was optimized for high carrier transit time-limited bandwidth. Photodiode integration was achieved using a scalable wafer die bonding approach that is fully compatible with the LNOI platform.
Photonics Research
- Publication Date: May. 12, 2022
- Vol.10 Issue, 6 06001338 (2022)
Quantum Optics
Spectrally multiplexed indistinguishable single-photon generation at telecom-bandHao Yu, Chenzhi Yuan, Ruiming Zhang, Zichang Zhang, Hao Li, You Wang, Guangwei Deng, Lixing You, Haizhi Song, Zhiming Wang, Guang-Can Guo, and Qiang Zhou
Heralded single-photon source (HSPS) intrinsically suffers from the trade-off between the heralded single-photon rate and the single-photon purity. To break through this trade-off, one can apply multiplexing technology in different degrees of freedom that significantly improves the performance of the HSPS. Here, we propose a 1.5 μm chip-scale HSPS on lithium niobate on insulator by employing spectral multiplexing and active feed-forward spectral manipulating, and we demonstrate a proof-of-principle experiment with discrete fiber-based components. With continuous-wave laser pumping and three spectral modes multiplexed, our experimental results show that the spectral multiplexing improves the heralded single-photon rate by near threefold while keeping the
Photonics Research
- Publication Date: May. 20, 2022
- Vol.10 Issue, 6 06001417 (2022)
Quantum Optics
Experimental quantum simulation of dynamic localization on curved photonic latticesHao Tang, Tian-Yu Wang, Zi-Yu Shi, Zhen Feng, Yao Wang, Xiao-Wen Shang, Jun Gao, Zhi-Qiang Jiao, Zhan-Ming Li, Yi-Jun Chang, Wen-Hao Zhou, Yong-Heng Lu, Yi-Lin Yang, Ruo-Jing Ren, Lu-Feng Qiao, and Xian-Min Jin
Dynamic localization, which originates from the phenomena of particle evolution suppression under an externally applied AC electric field, has been simulated by suppressed light evolution in periodically curved photonic arrays. However, experimental studies on their quantitative dynamic transport properties and application for quantum information processing are rare. Here we fabricate one-dimensional and hexagonal two-dimensional arrays both with sinusoidal curvatures. We successfully observe the suppressed single-photon evolution patterns, and for the first time, to the best of our knowledge, measure the variances to study their transport properties. For one-dimensional arrays, the measured variances match both the analytical electric-field calculation and the quantum walk Hamiltonian engineering approach. For hexagonal arrays as anisotropic effective couplings in four directions are mutually dependent, the analytical approach suffers, whereas quantum walk conveniently incorporates all anisotropic coupling coefficients in the Hamiltonian and solves its exponential as a whole, yielding consistent variances with our experimental results. Furthermore, we implement a nearly complete localization to show that it can preserve both the initial injection and the wave packet after some evolution, acting as a memory of a flexible time scale in integrated photonics. We demonstrate a useful quantum simulation of dynamic localization for studying their anisotropic transport properties and a promising application of dynamic localization as a building block for quantum information processing in integrated photonics.Dynamic localization, which originates from the phenomena of particle evolution suppression under an externally applied AC electric field, has been simulated by suppressed light evolution in periodically curved photonic arrays. However, experimental studies on their quantitative dynamic transport properties and application for quantum information processing are rare. Here we fabricate one-dimensional and hexagonal two-dimensional arrays both with sinusoidal curvatures. We successfully observe the suppressed single-photon evolution patterns, and for the first time, to the best of our knowledge, measure the variances to study their transport properties. For one-dimensional arrays, the measured variances match both the analytical electric-field calculation and the quantum walk Hamiltonian engineering approach. For hexagonal arrays as anisotropic effective couplings in four directions are mutually dependent, the analytical approach suffers, whereas quantum walk conveniently incorporates all anisotropic coupling coefficients in the Hamiltonian and solves its exponential as a whole, yielding consistent variances with our experimental results. Furthermore, we implement a nearly complete localization to show that it can preserve both the initial injection and the wave packet after some evolution, acting as a memory of a flexible time scale in integrated photonics. We demonstrate a useful quantum simulation of dynamic localization for studying their anisotropic transport properties and a promising application of dynamic localization as a building block for quantum information processing in integrated photonics.
Photonics Research
- Publication Date: May. 20, 2022
- Vol.10 Issue, 6 06001430 (2022)
Research ArticlesVol.10, Iss.5-May..1,2022
Errata
Single-shot 3D tracking based on polarization multiplexed Fourier-phase camera: erratumJiajie Teng, Chengyang Hu, Honghao Huang, Minghua Chen, Sigang Yang, and Hongwei Chen
This erratum corrects Fig. 5 in Photon. Res. 9 , 1924 (2021 )PRHEIZ 2327-9125 10.1364/PRJ.432292 Photon. Res. 9 , 1924 (2021 )PRHEIZ 2327-9125 10.1364/PRJ.432292
Photonics Research
- Publication Date: Apr. 29, 2022
- Vol.10 Issue, 5 05001307 (2022)
Fiber Optics and Optical Communications
Electrically induced dynamic Fano-like resonance in a graphene-coated fiber gratingBiqiang Jiang, Xiaoming Zhang, Ailun Li, Yueguo Hou, Zhen Hao, Xuetao Gan, and Jianlin Zhao
We created an all-fiber solution for fast, continuous, and controllable tuning of Fano-like resonance. By embedding a graphene-coated fiber Bragg grating into one arm of a Mach–Zehnder interferometer, the narrow Bragg resonance interacts with a broad interference spectrum, forming a sharp asymmetric Fano-like resonance line shape. With the application of an electrical voltage over the graphene layer, the generated Joule heating shifts the Bragg resonance and consequently tunes the asymmetric Fano-like resonance line shape to a symmetric dip or electromagnetically induced transparency-like peak. Further, by exploiting two modulated states with reversed Fano-like resonance line shapes, an optical switch can operate with an extinction ratio of 9 dB. The well-engineered Fano-like resonance in an all-fiber structure opens up new horizons for applications of fiber gratings in optical signal processing, slow-light lasing, and fiber sensing.We created an all-fiber solution for fast, continuous, and controllable tuning of Fano-like resonance. By embedding a graphene-coated fiber Bragg grating into one arm of a Mach–Zehnder interferometer, the narrow Bragg resonance interacts with a broad interference spectrum, forming a sharp asymmetric Fano-like resonance line shape. With the application of an electrical voltage over the graphene layer, the generated Joule heating shifts the Bragg resonance and consequently tunes the asymmetric Fano-like resonance line shape to a symmetric dip or electromagnetically induced transparency-like peak. Further, by exploiting two modulated states with reversed Fano-like resonance line shapes, an optical switch can operate with an extinction ratio of 9 dB. The well-engineered Fano-like resonance in an all-fiber structure opens up new horizons for applications of fiber gratings in optical signal processing, slow-light lasing, and fiber sensing.
Photonics Research
- Publication Date: Apr. 14, 2022
- Vol.10 Issue, 5 05001238 (2022)
Imaging Systems, Microscopy, and Displays
Improving signal-to-background ratio by orders of magnitude in high-speed volumetric imaging in vivo by robust Fourier light field microscopyJiazhen Zhai, Ruheng Shi, and Lingjie Kong
Fourier light field microscopy (FLFM) shows great potential in high-speed volumetric imaging of biodynamics. However, due to the inherent disadvantage of wide-field illumination, it suffers from intense background, arising from out of the depth-of-field signal and tissue scattered noise. The background will not only deteriorate the image contrast, making quantitative measurement difficult, but also introduce artifacts, especially in functional imaging of the neuronal network activity in vivo. Here, we propose the robust Fourier light field microscopy (RFLFM), which suppresses the background in FLFM by introducing structured illumination and computational reconstruction based on HiLo. The superior performance of RFLFM is verified by volumetric imaging of biological dynamics in larval zebrafish and mouse in vivo, at a volumetric imaging rate up to 33.3 Hz. The statistical results show that the fluorescence background can be significantly depressed, with the signal-to-background ratio improved by orders of magnitude and the whole image contrast improved by as much as
Photonics Research
- Publication Date: Apr. 21, 2022
- Vol.10 Issue, 5 05001255 (2022)
Imaging Systems, Microscopy, and Displays
Polarization microwave-induced thermoacoustic imaging for quantitative characterization of deep biological tissue microstructuresYujing Li, Shanxiang Zhang, Linghua Wu, Zhongwen Cheng, Zhenhui Zhang, Haohao Wang, Shuxiang Zhao, Mingyang Ren, Sihua Yang, Da Xing, and Huan Qin
Polarization optical imaging can be used to characterize anisotropy in biological tissue microstructures and has been demonstrated to be a powerful tool for clinical diagnosis. However, the approach is limited by an inability to image targets deeper than
Photonics Research
- Publication Date: Apr. 29, 2022
- Vol.10 Issue, 5 05001297 (2022)
Imaging Systems, Microscopy, and Displays
Miniaturized structured illumination microscopy with diffractive opticsGuoxuan Liu, Ning Xu, Huaidong Yang, Qiaofeng Tan, and Guofan Jin
Structured illumination microscopy (SIM) is an advanced microscope system that provides superresolution capability with excellent imaging speed, which has become a practical tool for live-cell imaging. However, the bulky size is blocking the application of SIM in wider study fields and scenarios. Here, we developed a miniaturized SIM (Mini SIM) system that provided periodic illumination using a diffractive optical element (DOE) for the first time. This optimized phase-only DOE generated the two-dimensional sinusoidal illumination by optical Fourier transform with an illuminating objective lens, which substantially simplified and miniaturized the illumination system. We built up a Mini SIM prototype and demonstrated lateral superresolution imaging of fluorescence beads and A549 cell slides. The proposed Mini SIM greatly simplifies the experimental setup and may lead to important applications in bio-imaging.Structured illumination microscopy (SIM) is an advanced microscope system that provides superresolution capability with excellent imaging speed, which has become a practical tool for live-cell imaging. However, the bulky size is blocking the application of SIM in wider study fields and scenarios. Here, we developed a miniaturized SIM (Mini SIM) system that provided periodic illumination using a diffractive optical element (DOE) for the first time. This optimized phase-only DOE generated the two-dimensional sinusoidal illumination by optical Fourier transform with an illuminating objective lens, which substantially simplified and miniaturized the illumination system. We built up a Mini SIM prototype and demonstrated lateral superresolution imaging of fluorescence beads and A549 cell slides. The proposed Mini SIM greatly simplifies the experimental setup and may lead to important applications in bio-imaging.
Photonics Research
- Publication Date: Apr. 29, 2022
- Vol.10 Issue, 5 05001317 (2022)
Instrumentation and Measurements
Measurement of sub-fm/Hz1/2 displacement spectral densities in ultrahigh-Q single-crystal microcavities with hertz-level lasersYoon-Soo Jang, Jinkang Lim, Wenting Wang, Seung-Woo Kim, Anatoliy Savchenkov, Andrey B. Matsko, and Chee Wei Wong
Tracing a resonance frequency of a high quality factor (Q) optical cavity facilitates subpicometer displacement measurements of the optical cavity via Pound–Drever–Hall (PDH) locking scheme, tightly synchronizing a laser frequency to the optical cavity. Here we present observations of subfemtometer displacements on a ultrahigh-Q single-crystal
Photonics Research
- Publication Date: Apr. 14, 2022
- Vol.10 Issue, 5 05001202 (2022)
Instrumentation and Measurements
Intensity diffusion: a concealed cause of fringe distortion in fringe projection profilometryZheng Sun, Minghui Duan, Yabing Zheng, Yi Jin, Xin Fan, and Jinjin Zheng
Fringe projection profilometry (FPP) is widely used in optical three-dimensional (3D) measurements because of its high stability. In FPP, fringe distortion is an inevitable and highly complex systematic error that significantly reduces the 3D measurement accuracy. At this point, the existing causes of fringe distortion represented by gamma distortion, high-order harmonics, and image saturation have been effectively analyzed and compensated to restore high-quality fringe images. In this paper, we innovatively reveal a concealed cause of fringe distortion, i.e., intensity diffusion across pixels, which is induced by photocarrier diffusion between photodiodes. To the best of our knowledge, intensity diffusion has not been studied in the field of fringe restoration. Based on the motion of photocarrier diffusion, we theoretically analyze the mechanism of how the intensity diffusion affects FPP. Subsequently, an intensity diffusion model is established for quantifying the diffused intensity in each pixel, and an intensity diffusion correction algorithm is presented to remove the diffused intensity from the fringe images and correct the fringe distortion. Experiments demonstrate the impact of intensity diffusion on FPP, and the 3D measurement results prove the effectiveness of the proposed methods on improving the 3D measurement accuracy by correcting the fringe distortion.Fringe projection profilometry (FPP) is widely used in optical three-dimensional (3D) measurements because of its high stability. In FPP, fringe distortion is an inevitable and highly complex systematic error that significantly reduces the 3D measurement accuracy. At this point, the existing causes of fringe distortion represented by gamma distortion, high-order harmonics, and image saturation have been effectively analyzed and compensated to restore high-quality fringe images. In this paper, we innovatively reveal a concealed cause of fringe distortion, i.e., intensity diffusion across pixels, which is induced by photocarrier diffusion between photodiodes. To the best of our knowledge, intensity diffusion has not been studied in the field of fringe restoration. Based on the motion of photocarrier diffusion, we theoretically analyze the mechanism of how the intensity diffusion affects FPP. Subsequently, an intensity diffusion model is established for quantifying the diffused intensity in each pixel, and an intensity diffusion correction algorithm is presented to remove the diffused intensity from the fringe images and correct the fringe distortion. Experiments demonstrate the impact of intensity diffusion on FPP, and the 3D measurement results prove the effectiveness of the proposed methods on improving the 3D measurement accuracy by correcting the fringe distortion.
Photonics Research
- Publication Date: Apr. 14, 2022
- Vol.10 Issue, 5 05001210 (2022)
Integrated Optics
Machine-learning-empowered multispectral metafilm with reduced radar cross section, low infrared emissivity, and visible transparencyRuichao Zhu, Jiafu Wang, Jinming Jiang, Cuilian Xu, Che Liu, Yuxiang Jia, Sai Sui, Zhongtao Zhang, Tonghao Liu, Zuntian Chu, Jun Wang, Tie Jun Cui, and Shaobo Qu
For camouflage applications, the performance requirements for metamaterials in different electromagnetic spectra are usually contradictory, which makes it difficult to develop satisfactory design schemes with multispectral compatibility. Fortunately, empowered by machine learning, metamaterial design is no longer limited to directly solving Maxwell’s equations. The design schemes and experiences of metamaterials can be analyzed, summarized, and learned by computers, which will significantly improve the design efficiency for the sake of practical engineering applications. Here, we resort to the machine learning to solve the multispectral compatibility problem of metamaterials and demonstrate the design of a new metafilm with multiple mechanisms that can realize small microwave scattering, low infrared emissivity, and visible transparency simultaneously using a multilayer backpropagation neural network. The rapid evolution of structural design is realized by establishing a mapping between spectral curves and structural parameters. By training the network with different materials, the designed network is more adaptable. Through simulations and experimental verifications, the designed architecture has good accuracy and robustness. This paper provides a facile method for fast designs of multispectral metafilms that can find wide applications in satellite solar panels, aircraft windows, and others.For camouflage applications, the performance requirements for metamaterials in different electromagnetic spectra are usually contradictory, which makes it difficult to develop satisfactory design schemes with multispectral compatibility. Fortunately, empowered by machine learning, metamaterial design is no longer limited to directly solving Maxwell’s equations. The design schemes and experiences of metamaterials can be analyzed, summarized, and learned by computers, which will significantly improve the design efficiency for the sake of practical engineering applications. Here, we resort to the machine learning to solve the multispectral compatibility problem of metamaterials and demonstrate the design of a new metafilm with multiple mechanisms that can realize small microwave scattering, low infrared emissivity, and visible transparency simultaneously using a multilayer backpropagation neural network. The rapid evolution of structural design is realized by establishing a mapping between spectral curves and structural parameters. By training the network with different materials, the designed network is more adaptable. Through simulations and experimental verifications, the designed architecture has good accuracy and robustness. This paper provides a facile method for fast designs of multispectral metafilms that can find wide applications in satellite solar panels, aircraft windows, and others.
Photonics Research
- Publication Date: Apr. 06, 2022
- Vol.10 Issue, 5 05001146 (2022)
Integrated Optics
Topological protection of partially coherent lightEditors' PickKonrad Tschernig, Gabriel Martinez-Niconoff, Kurt Busch, Miguel A. Bandres, and Armando Perez-Leija
Topological physics exploits concepts from geometry and topology to implement systems capable of guiding waves in an unprecedented fashion. These ideas have led to the development of photonic topological insulators, which are optical systems whose eigenspectral topology allows the creation of light states that propagate along the edge of the system without any coupling into the bulk or backscattering even in the presence of disorder. Indeed, topological protection is a fully coherent effect, and it is not clear to what extent topological effects endure when the wavefronts become partially coherent. Here, we study the interplay of topological protection and the degree of spatial coherence of classical light propagating in disordered photonic topological insulators. Our results reveal the existence of a well-defined spectral window in which partially coherent light is topologically protected. This opens up the design space to a wider selection of light sources, possibly yielding smaller, cheaper, and more robust devices based on the topological transport of light.Topological physics exploits concepts from geometry and topology to implement systems capable of guiding waves in an unprecedented fashion. These ideas have led to the development of photonic topological insulators, which are optical systems whose eigenspectral topology allows the creation of light states that propagate along the edge of the system without any coupling into the bulk or backscattering even in the presence of disorder. Indeed, topological protection is a fully coherent effect, and it is not clear to what extent topological effects endure when the wavefronts become partially coherent. Here, we study the interplay of topological protection and the degree of spatial coherence of classical light propagating in disordered photonic topological insulators. Our results reveal the existence of a well-defined spectral window in which partially coherent light is topologically protected. This opens up the design space to a wider selection of light sources, possibly yielding smaller, cheaper, and more robust devices based on the topological transport of light.
Photonics Research
- Publication Date: Apr. 14, 2022
- Vol.10 Issue, 5 05001223 (2022)
Integrated Optics
Soliton frequency comb generation in CMOS-compatible silicon nitride microresonatorsYaozu Xie, Jiaqi Li, Yanfeng Zhang, Zeru Wu, Shihao Zeng, Shuqing Lin, Zhaoyang Wu, Wenchao Zhou, Yujie Chen, and Siyuan Yu
The monolithic integration of soliton microcomb devices with active photonic components and high-frequency electronics is highly desirable for practical applications. Among many materials, silicon nitride (
Photonics Research
- Publication Date: Apr. 29, 2022
- Vol.10 Issue, 5 05001290 (2022)
Lasers and Laser Optics
Four-wave mixing in 1.3 μm epitaxial quantum dot lasers directly grown on siliconEditors' PickJianan Duan, Bozhang Dong, Weng W. Chow, Heming Huang, Shihao Ding, Songtao Liu, Justin C. Norman, John E. Bowers, and Frédéric Grillot
This work compares the four-wave mixing (FWM) effect in epitaxial quantum dot (QD) lasers grown on silicon with quantum well (QW) lasers. A comparison of theory and experiment results shows that the measured FWM coefficient is in good agreement with theoretical predictions. The gain in signal power is higher for p-doped QD lasers than for undoped lasers, despite the same FWM coefficient. Owing to the near-zero linewidth enhancement factor, QD lasers exhibit FWM coefficients and conversion efficiency that are more than one order of magnitude higher than those of QW lasers. Thus, this leads to self-mode locking in QD lasers. These findings are useful for developing on-chip sources for photonic integrated circuits on silicon.This work compares the four-wave mixing (FWM) effect in epitaxial quantum dot (QD) lasers grown on silicon with quantum well (QW) lasers. A comparison of theory and experiment results shows that the measured FWM coefficient is in good agreement with theoretical predictions. The gain in signal power is higher for p-doped QD lasers than for undoped lasers, despite the same FWM coefficient. Owing to the near-zero linewidth enhancement factor, QD lasers exhibit FWM coefficients and conversion efficiency that are more than one order of magnitude higher than those of QW lasers. Thus, this leads to self-mode locking in QD lasers. These findings are useful for developing on-chip sources for photonic integrated circuits on silicon.
Photonics Research
- Publication Date: Apr. 21, 2022
- Vol.10 Issue, 5 05001264 (2022)
Lasers and Laser Optics
High-performance distributed feedback quantum dot lasers with laterally coupled dielectric gratingsZhuohui Yang, Zhengqing Ding, Lin Liu, Hancheng Zhong, Sheng Cao, Xinzhong Zhang, Shizhe Lin, Xiaoying Huang, Huadi Deng, Ying Yu, and Siyuan Yu
The combination of grating-based frequency-selective optical feedback mechanisms, such as distributed feedback (DFB) or distributed Bragg reflector (DBR) structures, with quantum dot (QD) gain materials is a main approach towards ultrahigh-performance semiconductor lasers for many key novel applications, as either stand-alone sources or on-chip sources in photonic integrated circuits. However, the fabrication of conventional buried Bragg grating structures on GaAs, GaAs/Si, GaSb, and other material platforms has been met with major material regrowth difficulties. We report a novel and universal approach of introducing laterally coupled dielectric Bragg gratings to semiconductor lasers that allows highly controllable, reliable, and strong coupling between the grating and the optical mode. We implement such a grating structure in a low-loss amorphous silicon material alongside GaAs lasers with InAs/GaAs QD gain layers. The resulting DFB laser arrays emit at pre-designed 0.8 THz local area network wavelength division multiplexing frequency intervals in the 1300 nm band with record performance parameters, including sidemode suppression ratios as high as 52.7 dB, continuous-wave output power of 26.6 mW (room temperature) and 6 mW (at 55°C), and ultralow relative intensity noise (RIN) of
Photonics Research
- Publication Date: Apr. 29, 2022
- Vol.10 Issue, 5 05001271 (2022)
Lasers and Laser Optics
Ultra-broadband flat-top quantum dot comb lasersSpotlight on OpticsJing-Zhi Huang, Zi-Tao Ji, Jia-Jian Chen, Wen-Qi Wei, Jia-Le Qin, Zi-Hao Wang, Zhi-Yuan Li, Ting Wang, Xi Xiao, and Jian-Jun Zhang
A quantum dot (QD) mode-locked laser as an active comb generator takes advantage of its small footprint, low power consumption, large optical bandwidth, and high-temperature stability, which is an ideal multi-wavelength source for applications such as datacom, optical interconnects, and LIDAR. In this work, we report a fourth-order colliding pulse mode-locked laser (CPML) based on InAs/GaAs QD gain structure, which can generate ultra-stable optical frequency combs in the O-band with 100 GHz spacing at operation temperature up to 100°C. A record-high flat-top optical comb is achieved with 3 dB optical bandwidth of 11.5 nm (20 comb lines) at 25°C. The average optical linewidth of comb lines is measured as 440 kHz. Single-channel non-return-to-zero modulation rates of 70 Gbit/s and four-level pulse amplitude modulation of 40 GBaud/s are also demonstrated. To further extend the comb bandwidth, an array of QD-CPMLs driven at separate temperatures is proposed to achieve 36 nm optical bandwidth (containing 60 comb lines with 100 GHz mode spacing), capable of a total transmission capacity of 4.8 Tbit/s. The demonstrated results show the feasibility of using the QD-CPML as a desirable broadband comb source to build future large-bandwidth and power-efficient optical interconnects.A quantum dot (QD) mode-locked laser as an active comb generator takes advantage of its small footprint, low power consumption, large optical bandwidth, and high-temperature stability, which is an ideal multi-wavelength source for applications such as datacom, optical interconnects, and LIDAR. In this work, we report a fourth-order colliding pulse mode-locked laser (CPML) based on InAs/GaAs QD gain structure, which can generate ultra-stable optical frequency combs in the O-band with 100 GHz spacing at operation temperature up to 100°C. A record-high flat-top optical comb is achieved with 3 dB optical bandwidth of 11.5 nm (20 comb lines) at 25°C. The average optical linewidth of comb lines is measured as 440 kHz. Single-channel non-return-to-zero modulation rates of 70 Gbit/s and four-level pulse amplitude modulation of 40 GBaud/s are also demonstrated. To further extend the comb bandwidth, an array of QD-CPMLs driven at separate temperatures is proposed to achieve 36 nm optical bandwidth (containing 60 comb lines with 100 GHz mode spacing), capable of a total transmission capacity of 4.8 Tbit/s. The demonstrated results show the feasibility of using the QD-CPML as a desirable broadband comb source to build future large-bandwidth and power-efficient optical interconnects.
Photonics Research
- Publication Date: Apr. 29, 2022
- Vol.10 Issue, 5 05001308 (2022)
Nanophotonics and Photonic Crystals
Higher-order valley vortices enabled by synchronized rotation in a photonic crystalRui Zhou, Hai Lin, Yanjie Wu, Zhifeng Li, Zihao Yu, Y. Liu, and Dong-Hui Xu
Synchronized rotation of unit cells in a periodic structure provides a novel design perspective for manipulation of band topology. We then design a two-dimensional version of higher-order topological insulator (HOTI) by such rotation in a triangular photonic lattice with
Photonics Research
- Publication Date: Apr. 21, 2022
- Vol.10 Issue, 5 05001244 (2022)
Optical and Photonic Materials
Broadband NIR-emitting Te cluster-doped glass for smart light source towards night-vision and NIR spectroscopy applicationsLinling Tan, Yanqing Fu, Shiliang Kang, Lothar Wondraczek, Changgui Lin, and Yuanzheng Yue
Broadband near-infrared (NIR)-emitting materials are crucial components of the next generation of smart NIR light sources based on blue light-emitting diodes (LEDs). Here, we report a Te cluster-doped borate glass, which exhibits ultra-broadband emission around 980 nm with a full-width at half-maximum (FWHM) of 306 nm under blue light excitation. We propose adjustments of glass chemistry and processing condition as a means for topo-chemical tailoring of the NIR photoemission characteristics in such materials. Through implementing strongly reducing conditions during glass melting, Te clusters with broad NIR photoluminescence can be generated and stabilized once the melt is vitrified to the glassy state. Tunability of the NIR emission peak over the wavelength range of 904 to 1026 nm is possible in this way, allowing for fine adjustments of spectral properties relative to the stretching vibrations of common chemical bonds, for example, in water, proteins, and fats. This potentially enables high sensitivity in NIR spectroscopy. We further demonstrate potential application of glass-converted LEDs in night vision.Broadband near-infrared (NIR)-emitting materials are crucial components of the next generation of smart NIR light sources based on blue light-emitting diodes (LEDs). Here, we report a Te cluster-doped borate glass, which exhibits ultra-broadband emission around 980 nm with a full-width at half-maximum (FWHM) of 306 nm under blue light excitation. We propose adjustments of glass chemistry and processing condition as a means for topo-chemical tailoring of the NIR photoemission characteristics in such materials. Through implementing strongly reducing conditions during glass melting, Te clusters with broad NIR photoluminescence can be generated and stabilized once the melt is vitrified to the glassy state. Tunability of the NIR emission peak over the wavelength range of 904 to 1026 nm is possible in this way, allowing for fine adjustments of spectral properties relative to the stretching vibrations of common chemical bonds, for example, in water, proteins, and fats. This potentially enables high sensitivity in NIR spectroscopy. We further demonstrate potential application of glass-converted LEDs in night vision.
Photonics Research
- Publication Date: Apr. 14, 2022
- Vol.10 Issue, 5 05001187 (2022)
Optical Devices
Continuous-wave operation of 405 nm distributed Bragg reflector laser diodes based on GaN using 10th-order surface gratingsJ. H. Kang, H. Wenzel, E. Freier, V. Hoffmann, J. Fricke, O. Brox, M. Matalla, and S. Einfeldt
Single longitudinal mode continuous-wave operation of GaN-based distributed Bragg reflector (DBR) laser diodes with 10th-order surface gratings is demonstrated. The DBR consists of periodic V-shaped grooves on a 2 μm wide ridge waveguide fabricated by using electron-beam lithography and plasma etching. The effect of different lengths of the DBR section and the gain section on the device performance has been studied. Periodic mode hops to the adjacent longitudinal Fabry–Perot resonator mode at shorter wavelength have been observed when increasing the operation current. Between the mode hops, single longitudinal mode emission at around 405 nm is achieved with a full width at half-maximum of 0.03 nm. A linear redshift of the emission wavelength with increasing temperature of 0.019 nm/K was derived.Single longitudinal mode continuous-wave operation of GaN-based distributed Bragg reflector (DBR) laser diodes with 10th-order surface gratings is demonstrated. The DBR consists of periodic V-shaped grooves on a 2 μm wide ridge waveguide fabricated by using electron-beam lithography and plasma etching. The effect of different lengths of the DBR section and the gain section on the device performance has been studied. Periodic mode hops to the adjacent longitudinal Fabry–Perot resonator mode at shorter wavelength have been observed when increasing the operation current. Between the mode hops, single longitudinal mode emission at around 405 nm is achieved with a full width at half-maximum of 0.03 nm. A linear redshift of the emission wavelength with increasing temperature of 0.019 nm/K was derived.
Photonics Research
- Publication Date: Apr. 08, 2022
- Vol.10 Issue, 5 05001157 (2022)
Optical Devices
Impact of non-Hermitian mode interaction on inter-cavity light transferHyeon-Hye Yu, Sunjae Gwak, Jinhyeok Ryu, Hyundong Kim, Ji-Hwan Kim, Jung-Wan Ryu, Chil-Min Kim, and Chang-Hwan Yi
Understanding inter-site mutual mode interaction in coupled physical systems is essential to comprehend large compound systems, as this local interaction determines the successive multiple inter-site energy transfer efficiencies. In the present study, we demonstrate that only the non-Hermitian coupling can correctly account for the light transfer between two coupled optical cavities. We also reveal that the non-Hermitian coupling effect becomes crucial as the system dimension decreases. Our results provide important insight for handling general-coupled devices in the subwavelength regime.Understanding inter-site mutual mode interaction in coupled physical systems is essential to comprehend large compound systems, as this local interaction determines the successive multiple inter-site energy transfer efficiencies. In the present study, we demonstrate that only the non-Hermitian coupling can correctly account for the light transfer between two coupled optical cavities. We also reveal that the non-Hermitian coupling effect becomes crucial as the system dimension decreases. Our results provide important insight for handling general-coupled devices in the subwavelength regime.
Photonics Research
- Publication Date: Apr. 14, 2022
- Vol.10 Issue, 5 05001232 (2022)
Optoelectronics
Demonstration of electrically injected vertical-cavity surface-emitting lasers with post-supported high-contrast gratingsOn the CoverJing Zhang, Chenxi Hao, Wanhua Zheng, Dieter Bimberg, and Anjin Liu
We experimentally demonstrate for the first time to our knowledge electrically injected vertical-cavity surface-emitting lasers (VCSELs) with post-supported high-contrast gratings (HCGs) at 940 nm. The HCG-VCSELs have two posts to support the air-suspended HCGs, which are realized by simple fabrication without critical point drying. The HCG-VCSEL achieves a threshold current of about 0.65 mA and a side-mode suppression ratio of 43.6 dB under continuous-wave operation at 25°C. Theoretically the HCG-VCSEL with a
Photonics Research
- Publication Date: Apr. 14, 2022
- Vol.10 Issue, 5 05001170 (2022)
Optoelectronics
Epitaxial indium antimonide for multiband photodetection from IR to millimeter/terahertz waveJinchao Tong, Heng Luo, Fei Suo, Tianning Zhang, Dawei Zhang, and Dao Hua Zhang
Conventional photodetection converts light into electrical signals only in a single electromagnetic waveband. Multiband detection technology is highly desirable because it can handle multispectral information discrimination, identification, and processing. Current epitaxial solid-state multiband detection technologies are mainly within the IR wave range. Here, we report epitaxial indium antimonide on gallium arsenide for IR and millimeter/terahertz wave multiband photodetection. The photoresponse originates from interband transition in optoelectrical semiconductors for IR wave, and surface plasmon polaritons induced nonequilibrium electrons for a millimeter/terahertz wave. The detector shows a strong response for an IR wave with a cutoff wavelength of 6.85 μm and a blackbody detectivity of
Photonics Research
- Publication Date: Apr. 14, 2022
- Vol.10 Issue, 5 05001194 (2022)
Optoelectronics
Dissipative microwave photonic solitons in spontaneous frequency-hopping optoelectronic oscillatorsTengfei Hao, Hao Ding, Wei Li, Ninghua Zhu, Yitang Dai, and Ming Li
Dissipative solitons relying on the double balance between nonlinear and linear effects as well as cavity loss and gain have attracted increasing attention in recent years, since they give rise to novel operating states of various dissipative nonlinear systems. An optoelectronic oscillator (OEO) is a dissipative nonlinear microwave photonic system with a high quality factor that has been widely investigated for generating ultra-low noise single-frequency microwave signals. Here, we report a novel operating state of an OEO related to dissipative solitons, i.e., spontaneous frequency hopping related to the formation of dissipative microwave photonic solitons. In this operating state, dissipative microwave photonic solitons occur due to the double balance between nonlinear gain saturation and linear filtering as well as cavity loss and gain in the OEO cavity, creating spontaneous frequency-hopping microwave signals. The generation of wideband tunable frequency-hopping microwave signals with a fast frequency-hopping speed up to tens of nanoseconds is observed in the experiment, together with the corresponding soliton sequences. This work reveals a novel mechanism between the interaction of nonlinear and linear effects in an OEO cavity, extends the suitability and potential applications of solitons, and paves the way for a new class of soliton microwave photonic systems for the generation, processing, and control of microwave and RF signals.Dissipative solitons relying on the double balance between nonlinear and linear effects as well as cavity loss and gain have attracted increasing attention in recent years, since they give rise to novel operating states of various dissipative nonlinear systems. An optoelectronic oscillator (OEO) is a dissipative nonlinear microwave photonic system with a high quality factor that has been widely investigated for generating ultra-low noise single-frequency microwave signals. Here, we report a novel operating state of an OEO related to dissipative solitons, i.e., spontaneous frequency hopping related to the formation of dissipative microwave photonic solitons. In this operating state, dissipative microwave photonic solitons occur due to the double balance between nonlinear gain saturation and linear filtering as well as cavity loss and gain in the OEO cavity, creating spontaneous frequency-hopping microwave signals. The generation of wideband tunable frequency-hopping microwave signals with a fast frequency-hopping speed up to tens of nanoseconds is observed in the experiment, together with the corresponding soliton sequences. This work reveals a novel mechanism between the interaction of nonlinear and linear effects in an OEO cavity, extends the suitability and potential applications of solitons, and paves the way for a new class of soliton microwave photonic systems for the generation, processing, and control of microwave and RF signals.
Photonics Research
- Publication Date: Apr. 29, 2022
- Vol.10 Issue, 5 05001280 (2022)
Silicon Photonics
Discretization of annular-ring diffraction pattern for large-scale photonics beamformingEditors' PickAroutin Khachaturian, Reza Fatemi, Artsroun Darbinian, and Ali Hajimiri
A solid-state active beamformer based on the annular-ring diffraction pattern is demonstrated in an integrated photonic platform. Such a circularly symmetric annular-ring aperture achieves a radiating element limited field of view. Furthermore, it is demonstrated that a multi-annular-ring aperture with a fixed linear density of elements maintains the beam efficiency for larger apertures while reducing the beamwidth and side-lobe level. A 255-element multi-annular-ring optical phased array with active beamforming is implemented in a standard photonics process. A total of 510 phase and amplitude modulators enable beamforming and beam steering using this aperture. A row–column drive methodology reduces the required electrical drivers by more than a factor of 5.A solid-state active beamformer based on the annular-ring diffraction pattern is demonstrated in an integrated photonic platform. Such a circularly symmetric annular-ring aperture achieves a radiating element limited field of view. Furthermore, it is demonstrated that a multi-annular-ring aperture with a fixed linear density of elements maintains the beam efficiency for larger apertures while reducing the beamwidth and side-lobe level. A 255-element multi-annular-ring optical phased array with active beamforming is implemented in a standard photonics process. A total of 510 phase and amplitude modulators enable beamforming and beam steering using this aperture. A row–column drive methodology reduces the required electrical drivers by more than a factor of 5.
Photonics Research
- Publication Date: Apr. 14, 2022
- Vol.10 Issue, 5 05001177 (2022)
Surface Optics and Plasmonics
Multidimensional trapping by dual-focusing cylindrical vector beams with all-silicon metalensJia-Lu Zhu, Ren-Chao Jin, Li-Li Tang, Zheng-Gao Dong, Jia-Qi Li, and Jin Wang
Dual-focusing effect with a cylindrical vector-light characteristic (i.e., radial and azimuthal polarizations) is theoretically proposed and numerically demonstrated by spin-decoupled phase control with all-silicon metalens. Attributed to the polarization dependence, the pair of focusing cylindrical vector beams can be interchanged by orthogonally switching the polarization of incident light. We demonstrate the unique contributions of focused radial and azimuthal vector beams to longitudinal and transverse optical forces on glass spheres, respectively, by calculations based on the Maxwell stress tensor. This paper presents the use of all-silicon metalens with highly-compact vector beams, promising for applications such as multidimensional optical trapping.Dual-focusing effect with a cylindrical vector-light characteristic (i.e., radial and azimuthal polarizations) is theoretically proposed and numerically demonstrated by spin-decoupled phase control with all-silicon metalens. Attributed to the polarization dependence, the pair of focusing cylindrical vector beams can be interchanged by orthogonally switching the polarization of incident light. We demonstrate the unique contributions of focused radial and azimuthal vector beams to longitudinal and transverse optical forces on glass spheres, respectively, by calculations based on the Maxwell stress tensor. This paper presents the use of all-silicon metalens with highly-compact vector beams, promising for applications such as multidimensional optical trapping.
Photonics Research
- Publication Date: Apr. 08, 2022
- Vol.10 Issue, 5 05001162 (2022)
Next-generation Silicon Photonics (2022)
Submission Open:1 July 2021; Submission Deadline: 30 September 2021
Editor (s):
Soliton frequency comb generation in CMOS-compatible silicon nitride microresonators
Vol. 10, Issue 5, 05001290 (2022)
High-performance distributed feedback quantum dot lasers with laterally coupled dielectric gratings
Vol. 10, Issue 5, 05001271 (2022)
High-throughput microfabrication of axially tunable helicesEditors' Pick
Vol. 10, Issue 2, 02000303 (2022)
Mimicking the gravitational effect with gradient index lenses in geometrical optics
Vol. 9, Issue 7, 07001197 (2021)
Spin-decoupled metalens with intensity-tunable multiple focal pointsOn the Cover
Vol. 9, Issue 6, 06001019 (2021)
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