2021年 第2卷  第1期

Domain multiplexed computer-generated holography by embedded wavevector filtering algorithm
Lin Wu, Ziyang Zhang
2021, 2(1) doi: 10.1186/s43074-020-00023-9
Computer-generated holography can obtain the wavefront required for constructing arbitrary intensity distributions in space. Currently, speckle noises in holography remain an issue for most computational methods. In addition, there lacks a multiplexing technology by which images from a single hologram and light source can be switched by a lens. In this work, we first come up with a new algorithm to generate holograms to project smoother images by wavevector filtering. Thereupon, we propose a unique multiplexing scheme enabled by a Fourier lens, as the incident light can be decomposed either by a superposition of spherical waves or plane waves. Different images are obtained experimentally in the spatial and wavevector domains, switchable by a lens. The embedded wavevector filtering algorithm provides a new prospective for speckle suppression without the need for postprocessing. The multiplexing technology can double the capacity of current holographic systems and exhibits potential for various interesting display applications.
Optical waveguides based on one-dimensional organic crystals
Song Chen, Ming-Peng Zhuo, Xue-Dong Wang, Guo-Qing Wei, Liang-Sheng Liao
2021, 2(1) doi: 10.1186/s43074-021-00024-2

Optical waveguide of organic micro/nanocrystals is one of crucial elements in miniaturized integrated photonics. One-dimensional (1D) organic crystals with various optical features have attracted increasing interests towards promising photonic devices, such as multichannel signal converter, organic field-effect optical waveguide, sensitive detector, and optical logic gate. Therefore, a summary about the 1D organic micro/nanocrystals based optical waveguide is important for the rational design and fabrication of novel optical devices towards optoelectronics applications. Herein, recent advances of optical waveguide based on 1D organic micro/nanocrystals with solid, flexible, hollow, uniformly doped, core-shell, multiblock and branched structures are summarized from the aspects of the waveguide properties and applications in photonic devices. Furthermore, we presented our personal view about the expectation of future development in 1D organic optical waveguide for the photonic applications.

Graphical abstract

Nonlinear meta-optics towards applications
Yun Zhao, Yuanmu Yang, Hong-Bo Sun
2021, 2(1) doi: 10.1186/s43074-021-00025-1
Nonlinear optical effects have enabled numerous applications such as laser frequency conversion, ultrafast electro-optical, and all-optical modulation. Both gaseous and bulk media have conventionally been used for free-space nonlinear optical applications, yet they often require complex phase-matching techniques for efficient operation and may have limited operation bandwidth due to the material absorption. In the last decade, meta-optics made of subwavelength antennas or films have emerged as novel nonlinear optical media that may potentially overcome certain limitations of bulk crystals. Due to resonant enhancements of the pump laser field as well as the use of materials with extreme nonlinearity such as epsilon-near-zero materials, meta-optics can achieve strong nonlinear responses with a subwavelength thickness. Here, we review several nonlinear optical applications, such as electric-field-induced second-harmonic generation, entangled photon pair generation, terahertz generation, all-optical modulation, and high-harmonic generation that we envision meta-optics may have distinct advantages over their bulk counterparts. We outline the challenges still faced by nonlinear meta-optics and point out some potential directions.
Ultra-short-pulse high-average-power megahertz-repetition-rate coherent extreme-ultraviolet light source
Robert Klas, Alexander Kirsche, Martin Gebhardt, Joachim Buldt, Henning Stark, Steffen Hädrich, Jan Rothhardt, Jens Limpert
2021, 2(1) doi: 10.1186/s43074-021-00028-y
High harmonic generation (HHG) enables coherent extreme-ultraviolet (XUV) radiation with ultra-short pulse duration in a table-top setup. This has already enabled a plethora of applications. Nearly all of these applications would benefit from a high photon flux to increase the signal-to-noise ratio and decrease measurement times. In addition, shortest pulses are desired to investigate fastest dynamics in fields as diverse as physics, biology, chemistry and material sciences. In this work, the up-to-date most powerful table-top XUV source with 12.9 ± 3.9 mW in a single harmonic line at 26.5 eV is demonstrated via HHG of a frequency-doubled and post-compressed fibre laser. At the same time the spectrum supports a Fourier-limited pulse duration of sub-6 fs in the XUV, which allows accessing ultrafast dynamics with an order of magnitude higher photon flux than previously demonstrated. This concept will greatly advance and facilitate applications of XUV radiation in science and technology and enable photon-hungry ultrafast studies.
Research progress in optical neural networks: theory, applications and developments
Jia Liu, Qiuhao Wu, Xiubao Sui, Qian Chen, Guohua Gu, Liping Wang, Shengcai Li
2021, 2(1) doi: 10.1186/s43074-021-00026-0
With the advent of the era of big data, artificial intelligence has attracted continuous attention from all walks of life, and has been widely used in medical image analysis, molecular and material science, language recognition and other fields. As the basis of artificial intelligence, the research results of neural network are remarkable. However, due to the inherent defect that electrical signal is easily interfered and the processing speed is proportional to the energy loss, researchers have turned their attention to light, trying to build neural networks in the field of optics, making full use of the parallel processing ability of light to solve the problems of electronic neural networks. After continuous research and development, optical neural network has become the forefront of the world. Here, we mainly introduce the development of this field, summarize and compare some classical researches and algorithm theories, and look forward to the future of optical neural network.
Optical coherence encryption with structured random light
Deming Peng, Zhaofeng Huang, Yonglei Liu, Yahong Chen, Fei Wang, Sergey A. Ponomarenko, Yangjian Cai
2021, 2(1) doi: 10.1186/s43074-021-00027-z
Information encryption with optical technologies has become increasingly important due to remarkable multidimensional capabilities of light fields. However, the optical encryption protocols proposed to date have been primarily based on the first-order field characteristics, which are strongly affected by interference effects and make the systems become quite unstable during light–matter interaction. Here, we introduce an alternative optical encryption protocol whereby the information is encoded into the second-order spatial coherence distribution of a structured random light beam via a generalized van Cittert–Zernike theorem. We show that the proposed approach has two key advantages over its conventional counterparts. First, the complexity of measuring the spatial coherence distribution of light enhances the encryption protocol security. Second, the relative insensitivity of the second-order statistical characteristics of light to environmental noise makes the protocol robust against the environmental fluctuations, e.g, the atmospheric turbulence. We carry out experiments to demonstrate the feasibility of the coherence-based encryption method with the aid of a fractional Fourier transform. Our results open up a promising avenue for further research into optical encryption in complex environments.
Displacement-mediated bound states in the continuum in all-dielectric superlattice metasurfaces
Tan Shi, Zi-Lan Deng, Qing-An Tu, Yaoyu Cao, Xiangping Li
2021, 2(1) doi: 10.1186/s43074-021-00029-x
Bound states in the continuum (BICs) are localized states coexisting with extended waves inside the continuous spectrum range, which have infinite lifetimes without any radiation. To extract high-Q quasi-BIC resonances from the symmetry-protected BIC for practical applications, symmetry-breaking approaches are usually exploited, either by slightly breaking the excitation field symmetry or structure symmetry. Here, we introduce an all-dielectric superlattice metasurface that can symmetry-compatibly convert BIC states into high-Q quasi-BIC modes based on the guided-mode resonance coupling by relative displacement tuning. The metasurface is composed of a superlattice of multiple nanobeams, supporting both magnetic mode and toroidal mode with large tunability. Both modes can interact with the incident continuum by mediating the displacement between nanobeams, which empowers dual asymmetric Fano resonances with high Q-factors. The bandwidth of the toroidal mode under y-polarized incidences and that of the magnetic mode under x-polarized incidences can be readily tuned by the local displacement between nanobeams in each unit cell. Such displacement-mediated BIC resonance is promising for various applications such as bio-molecule sensing and low threshold lasing.
Deep learning wavefront sensing and aberration correction in atmospheric turbulence
Kaiqiang Wang, MengMeng Zhang, Ju Tang, Lingke Wang, Liusen Hu, Xiaoyan Wu, Wei Li, Jianglei Di, Guodong Liu, Jianlin Zhao
2021, 2(1) doi: 10.1186/s43074-021-00030-4
Deep learning neural networks are used for wavefront sensing and aberration correction in atmospheric turbulence without any wavefront sensor (i.e. reconstruction of the wavefront aberration phase from the distorted image of the object). We compared and found the characteristics of the direct and indirect reconstruction ways: (i) directly reconstructing the aberration phase; (ii) reconstructing the Zernike coefficients and then calculating the aberration phase. We verified the generalization ability and performance of the network for a single object and multiple objects. What’s more, we verified the correction effect for a turbulence pool and the feasibility for a real atmospheric turbulence environment.
Mid-infrared supercontinuum generation in chalcogenide glass fibers: a brief review
Yingying Wang, Shixun Dai
2021, 2(1) doi: 10.1186/s43074-021-00031-3
Chalcogenide (ChG) glasses have the characteristics of a wide transparency window (over 20 μm) and high optical nonlinearity (up to 103 times greater than that of silica glasses), exhibiting great advantages over silica and other soft glasses in optical property at mid-infrared (MIR) wavelength range. These make them excellent candidates for MIR supercontinuum (SC) generation. Over the past decades, great progress has been made in MIR SC generation based on ChG fibers in terms of spectral extension and output power improvement. In this paper, we introduce briefly the properties of ChG glasses and fibers including transmission, nonlinearity, and dispersion, etc. Recent progress in MIR SC generation based on ChG fibers is reviewed from the perspective of pump schemes. We also present novel ChG fibers such as As-free, Te-based, and chalcohalide fibers, which have been explored and employed as nonlinear fibers to achieve broadband SC generation. Moreover, the potential applications of MIR SC sources based on ChG fibers are discussed.
Dielectric metasurface zone plate for the generation of focusing vortex beams
Yufeng Hu, Xuan Liu, Mingke Jin, Yutao Tang, Xuecai Zhang, King Fai Li, Yan Zhao, Guixin Li, Jing Zhou
2021, 2(1) doi: 10.1186/s43074-021-00035-z
Vortex beams carrying orbital angular momentum have important applications in high dimensional optical information processing, manipulations of tiny particles, super-resolution imaging and so on. Among various optical components, metasurface represents an ideal platform for realizing vortex beams with multiple optical functionalities due to its strong ability in manipulating the phase, polarization and amplitude of light. A metasurface combing the functions of a lens and a vortex beam generator can greatly shrink the size of many optical systems. Here, we alternatively propose a new metasurface design based on the concept of a Fresnel zone plate to generate, focus the vortex beams, and perform on-axis interference between different vortex beams. These functions are experimentally demonstrated through encoding the spiral phase profiles into the odd and even zones of a dielectric metasurface. The proposed vortex beam generation strategy employs the advantages of both the Fresnel zone plate and the metasurface, and may open new routes for high-dimensional optical information processing.
Subwavelength silicon photonics for on-chip mode-manipulation
Chenlei Li, Ming Zhang, Hongnan Xu, Ying Tan, Yaocheng Shi, Daoxin Dai
2021, 2(1) doi: 10.1186/s43074-021-00032-2
On-chip mode-manipulation is one of the most important physical fundamentals for many photonic integrated devices and circuits. In the past years, great progresses have been achieved on subwavelength silicon photonics for on-chip mode-manipulation by introducing special subwavelength photonic waveguides. Among them, there are two popular waveguide structures available. One is silicon hybrid plasmonic waveguides (HPWGs) and the other one is silicon subwavelength-structured waveguides (SSWGs). In this paper, we focus on subwavelength silicon photonic devices and the applications with the manipulation of the effective indices, the modal field profiles, the mode dispersion, as well as the birefringence. First, a review is given about subwavelength silicon photonics for the fundamental-mode manipulation, including high-performance polarization-handling devices, efficient mode converters for chip-fiber edge-coupling, and ultra-broadband power splitters. Second, a review is given about subwavelength silicon photonics for the higher-order-mode manipulation, including multimode converters, multimode waveguide bends, and multimode waveguide crossing. Finally, some emerging applications of subwavelength silicon photonics for on-chip mode-manipulation are discussed.
Three-step one-way model in terahertz biomedical detection
Yan Peng, Jieli Huang, Jie Luo, Zhangfan Yang, Liping Wang, Xu Wu, Xiaofei Zang, Chen Yu, Min Gu, Qing Hu, Xicheng Zhang, Yiming Zhu, Songlin Zhuang
2021, 2(1) doi: 10.1186/s43074-021-00034-0
Terahertz technology has broad application prospects in biomedical detection. However, the mixed characteristics of actual samples make the terahertz spectrum complex and difficult to distinguish, and there is no practical terahertz detection method for clinical medicine. Here, we propose a three-step one-way terahertz model, presenting a detailed flow analysis of terahertz technology in the biomedical detection of renal fibrosis as an example: 1) biomarker determination: screening disease biomarkers and establishing the terahertz spectrum and concentration gradient; 2) mixture interference removal: clearing the interfering signals in the mixture for the biomarker in the animal model and evaluating and retaining the effective characteristic peaks; and 3) individual difference removal: excluding individual interference differences and confirming the final effective terahertz parameters in the human sample. The root mean square error of our model is three orders of magnitude lower than that of the gold standard, with profound implications for the rapid, accurate and early detection of diseases.
Recent progress in electro-optic polymer for ultra-fast communication
Fateh Ullah, Niping Deng, Feng Qiu
2021, 2(1) doi: 10.1186/s43074-021-00036-y
The rocketed development concerning electro-optic polymers fundamentally motivated by its pragmatic application in envisioning second-order nonlinear optics and waveguiding are cardinal. Modern synthetic strategies consigned an outstanding optical quality amorphous polymers with enhanced properties. Documented data revealed a huge progress in understanding their implementation, however challenges still exist regarding their temporal stabilities etc. This review delivers a brief investigation of nonlinear optical (NLO) polymer materials demonstrated over previous decades. Besides, their categorical explanation along with their structural architecting via engineering polymeric backbone or functionalization of the molecular entities have been reviewed. Correspondingly, their temporal and thermal stabilities accompanied by NLO characteristics features are also discussed.
Review: distributed time-domain sensors based on Brillouin scattering and FWM enhanced SBS for temperature, strain and acoustic wave detection
Xiaoyi Bao, Zichao Zhou, Yuan Wang
2021, 2(1) doi: 10.1186/s43074-021-00038-w
Distributed time-domain Brillouin scattering fiber sensors have been widely used to measure the changes of the temperature and strain. The linear dependence of the temperature and strain on the Brillouin frequency shift enabled the distributed temperature and strain sensing based on mapping of the Brillouin gain spectrum. In addition, an acoustic wave can be detected by the four wave mixing (FWM) associated SBS process, in which phase matching condition is satisfied via up-down conversion of SBS process through birefringence matching before and after the conversion process. Brillouin scattering can be considered as the scattering of a pump wave from a moving grating (acoustic phonon) which induces a Doppler frequency shift in the resulting Stokes wave. The frequency shift is dependent on many factors including the velocity of sound in the scattering medium as well as the index of refraction. Such a process can be used to monitor the gain of random fiber laser based on SBS, the distributed acoustic wave reflect the distributed SBS gain for random lasing radiation, as well as the relative intensity noise inside the laser gain medium. In this review paper, the distributed time-domain sensing system based on Brillouin scattering including Brillouin optical time-domain reflectometry (BOTDR), Brillouin optical time-domain analysis (BOTDA), and FWM enhanced SBS for acoustic wave detection are introduced for their working principles and recent progress. The distributed Brillouin sensors based on specialty fibers for simultaneous temperature and strain measurement are summarized. Applications for the Brillouin scattering time-domain sensors are briefly discussed.
From spectral broadening to recompression: dynamics of incoherent optical waves propagating in the fiber
Jun Ye, Xiaoya Ma, Yang Zhang, Jiangming Xu, Hanwei Zhang, Tianfu Yao, Jinyong Leng, Pu Zhou
2021, 2(1) doi: 10.1186/s43074-021-00037-x
Interplay between dispersion and nonlinearity in optical fibers is a fundamental research topic of nonlinear fiber optics. Here we numerically and experimentally investigate an incoherent continuous-wave (CW) optical field propagating in the fiber with normal dispersion, and introduce a distinctive spectral evolution that differs from the previous reports with coherent mode-locked fiber lasers and partially coherent Raman fiber lasers [Nat. Photonics 9, 608 (2015).]. We further reveal that the underlying physical mechanism is attributed to a novel interplay between group-velocity dispersion (GVD), self-phase modulation (SPM) and inverse four-wave mixing (IFWM), in which SPM and GVD are responsible for the first spectral broadening, while the following spectral recompression is due to the GVD-assisted IFWM, and the eventual stationary spectrum is owing to the dominant contribution of GVD effect. We believe this work can not only expand the light propagation in the fiber to a more general case and help advance the physical understanding of light propagation with different statistical properties, but also benefit the applications in sensing, telecommunications and fiber lasers.
High-speed visible light communication systems based on Si-substrate LEDs with multiple superlattice interlayers
Fangchen Hu, Shouqing Chen, Yuyi Zhang, Guoqiang Li, Peng Zou, Junwen Zhang, Chao Shen, Xiaolei Zhang, Jian Hu, Jianli Zhang, Zhixue He, Shaohua Yu, Fengyi Jiang, Nan Chi
2021, 2(1) doi: 10.1186/s43074-021-00039-9
High-speed visible light communication (VLC), as a cutting-edge supplementary solution in 6G to traditional radio-frequency communication, is expected to address the tension between continuously increased demand of capacity and currently limited supply of radio-frequency spectrum resource. The main driver behind the high-speed VLC is the presence of light emitting diode (LED) which not only offers energy-efficient lighting, but also provides a cost-efficient alternative to the VLC transmitter with superior modulation potential. Particularly, the InGaN/GaN LED grown on Si substrate is a promising VLC transmitter to simultaneously realize effective communication and illumination by virtue of beyond 10-Gbps communication capacity and Watt-level output optical power. In previous parameter optimization of Si-substrate LED, the superlattice interlayer (SL), especially its period number, is reported to be the key factor to improve the lighting performance by enhancing the wall-plug efficiency, but few efforts were made to investigate the influence of SLs on VLC performance. Therefore, to optimize the VLC performance of Si-substrate LEDs, we for the first time investigated the impact of the SL period number on VLC system through experiments and theoretical derivation. The results show that more SL period number is related to higher signal-to-noise ratio (SNR) via improving the wall-plug efficiency. In addition, by using Levin-Campello bit and power loading technology, we achieved a record-breaking data rate of 3.37 Gbps over 1.2-m free-space VLC link under given optimal SL period number, which, to the best of our knowledge, is the highest data rate for a Si-substrate LED-based VLC system.
Laser fabrication of modular superhydrophobic chips for reconfigurable assembly and self-propelled droplet manipulation
Huan Wang, Yong-Lai Zhang, Dong-Dong Han, Wei Wang, Hong-Bo Sun
2021, 2(1) doi: 10.1186/s43074-021-00033-1
Natural creatures that enables controllable liquid transport provides the inspiration for developing novel microfluidic devices by engineering functional surfaces with superwettability. However, towards microfluidic applications, the strict requirements of sophisticated droplet manipulation make it challenging to reach this end. In this work, we report a conceptually new self-propelled droplet manipulation strategy based on reconfigurable superhydrophobic chips. The modular droplet chip (MDC) is developed by laser embossing a series of superhydrophobic structures on elastomer jigsaws that act as functional units. MDC is potable since only gravity is used as the driving force for dynamic manipulation of liquid droplets, including droplets transporting, splitting, merging and bouncing without mass loss. The MDC demonstrated reasonable anti-cross-contamination property due to the water repellence of the superhydrophobicity. Modular assembly of MDC enables different chip functions including solution dilution, SERS detection, cell labeling and chemical synthesis. As a miniature and portable experimental platform, the MDC is promising for next-generation lab-on-a-chip systems.
Liquid crystal-amplified optofluidic biosensor for ultra-highly sensitive and stable protein assay
Ziyihui Wang, Yize Liu, Chaoyang Gong, Zhiyi Yuan, Liang Shen, Pengxiang Chang, Kun Liu, Tianhua Xu, Junfeng Jiang, Yu-Cheng Chen, Tiegen Liu
2021, 2(1) doi: 10.1186/s43074-021-00041-1
Protein assays show great importance in medical research and disease diagnoses. Liquid crystals (LCs), as a branch of sensitive materials, offer promising applicability in the field of biosensing. Herein, we developed an ultrasensitive biosensor for the detection of low-concentration protein molecules, employing LC-amplified optofluidic resonators. In this design, the orientation of LCs was disturbed by immobilized protein molecules through the reduction of the vertical anchoring force from the alignment layer. A biosensing platform based on the whispering-gallery mode (WGM) from the LC-amplified optofluidic resonator was developed and explored, in which the spectral wavelength shift was monitored as the sensing parameter. The microbubble structure provided a stable and reliable WGM resonator with a high Q factor for LCs. It is demonstrated that the wall thickness of the microbubble played a key role in enhancing the sensitivity of the LC-amplified WGM microcavity. It is also found that protein molecules coated on the internal surface of microbubble led to their interactions with laser beams and the orientation transition of LCs. Both effects amplified the target information and triggered a sensitive wavelength shift in WGM spectra. A detection limit of 1 fM for bovine serum albumin (BSA) was achieved to demonstrate the high-sensitivity of our sensing platform in protein assays. Compared to the detection using a conventional polarized optical microscope (POM), the sensitivity was improved by seven orders of magnitude. Furthermore, multiple types of proteins and specific biosensing were also investigated to verify the potential of LC-amplified optofluidic resonators in the biomolecular detection. Our studies indicate that LC-amplified optofluidic resonators offer a new solution for the ultrasensitive real-time biosensing and the characterization of biomolecular interactions.
Smart computational light microscopes (SCLMs) of smart computational imaging laboratory (SCILab)
Yao Fan, Jiaji Li, Linpeng Lu, Jiasong Sun, Yan Hu, Jialin Zhang, Zhuoshi Li, Qian Shen, Bowen Wang, Runnan Zhang, Qian Chen, Chao Zuo
2021, 2(1) doi: 10.1186/s43074-021-00040-2
Computational microscopy, as a subfield of computational imaging, combines optical manipulation and image algorithmic reconstruction to recover multi-dimensional microscopic images or information of micro-objects. In recent years, the revolution in light-emitting diodes (LEDs), low-cost consumer image sensors, modern digital computers, and smartphones provide fertile opportunities for the rapid development of computational microscopy. Consequently, diverse forms of computational microscopy have been invented, including digital holographic microscopy (DHM), transport of intensity equation (TIE), differential phase contrast (DPC) microscopy, lens-free on-chip holography, and Fourier ptychographic microscopy (FPM). These computational microscopy techniques not only provide high-resolution, label-free, quantitative phase imaging capability but also decipher new and advanced biomedical research and industrial applications. Nevertheless, most computational microscopy techniques are still at an early stage of “proof of concept” or “proof of prototype” (based on commercially available microscope platforms). Translating those concepts to stand-alone optical instruments for practical use is an essential step for the promotion and adoption of computational microscopy by the wider bio-medicine, industry, and education community. In this paper, we present four smart computational light microscopes (SCLMs) developed by our laboratory, i.e., smart computational imaging laboratory (SCILab) of Nanjing University of Science and Technology (NJUST), China. These microscopes are empowered by advanced computational microscopy techniques, including digital holography, TIE, DPC, lensless holography, and FPM, which not only enables multi-modal contrast-enhanced observations for unstained specimens, but also can recover their three-dimensional profiles quantitatively. We introduce their basic principles, hardware configurations, reconstruction algorithms, and software design, quantify their imaging performance, and illustrate their typical applications for cell analysis, medical diagnosis, and microlens characterization.
The challenges of modern computing and new opportunities for optics
Chong Li, Xiang Zhang, Jingwei Li, Tao Fang, Xiaowen Dong
2021, 2(1) doi: 10.1186/s43074-021-00042-0
In recent years, the explosive development of artificial intelligence implementing by artificial neural networks (ANNs) creates inconceivable demands for computing hardware. However, conventional computing hardware based on electronic transistor and von Neumann architecture cannot satisfy such an inconceivable demand due to the unsustainability of Moore’s Law and the failure of Dennard’s scaling rules. Fortunately, analog optical computing offers an alternative way to release unprecedented computational capability to accelerate varies computing drained tasks. In this article, the challenges of the modern computing technologies and potential solutions are briefly explained in Chapter 1. In Chapter 2, the latest research progresses of analog optical computing are separated into three directions: vector/matrix manipulation, reservoir computing and photonic Ising machine. Each direction has been explicitly summarized and discussed. The last chapter explains the prospects and the new challenges of analog optical computing.
Spontaneous emission in micro- or nanophotonic structures
Zhiyuan Qian, Lingxiao Shan, Xinchen Zhang, Qi Liu, Yun Ma, Qihuang Gong, Ying Gu
2021, 2(1) doi: 10.1186/s43074-021-00043-z
Single-photon source in micro- or nanoscale is the basic building block of on-chip quantum information and scalable quantum network. Enhanced spontaneous emission based on cavity quantum electrodynamics (CQED) is one of the key principles of realizing single-photon sources fabricated by micro- or nanophotonic cavities. Here we mainly review the spontaneous emission of single emitters in micro- or nanostructures, such as whispering gallery microcavities, photonic crystals, plasmon nanostructures, metamaterials, and their hybrids. The researches have enriched light-matter interaction as well as made great influence in single-photon source, photonic circuit, and on-chip quantum information.
Intelligent designs in nanophotonics: from optimization towards inverse creation
Ning Wang, Wei Yan, Yurui Qu, Siqi Ma, Stan Z. Li, Min Qiu
2021, 2(1) doi: 10.1186/s43074-021-00044-y
Applying intelligence algorithms to conceive nanoscale meta-devices becomes a flourishing and extremely active scientific topic over the past few years. Inverse design of functional nanostructures is at the heart of this topic, in which artificial intelligence (AI) furnishes various optimization toolboxes to speed up prototyping of photonic layouts with enhanced performance. In this review, we offer a systemic view on recent advancements in nanophotonic components designed by intelligence algorithms, manifesting a development trend from performance optimizations towards inverse creations of novel designs. To illustrate interplays between two fields, AI and photonics, we take meta-atom spectral manipulation as a case study to introduce algorithm operational principles, and subsequently review their manifold usages among a set of popular meta-elements. As arranged from levels of individual optimized piece to practical system, we discuss algorithm-assisted nanophotonic designs to examine their mutual benefits. We further comment on a set of open questions including reasonable applications of advanced algorithms, expensive data issue, and algorithm benchmarking, etc. Overall, we envision mounting photonic-targeted methodologies to substantially push forward functional artificial meta-devices to profit both fields.