reviews

Two-dimensional material photodetector for hybrid silicon photonics
HU Si-qi, TIAN Rui-juan, GAN Xue-tao
2021, 14(5): 1039-1055. doi: 10.37188/CO.2021-0003
Abstract:
Two-dimensional (2D) materials provide new development opportunities for silicon-based integrated optoelectronic devices due to their unique structure and excellent electronic and optoelectronic properties. In recent years, 2D material-based photodetectors for hybrid-integrated silicon photonics have been widely studied. Based on the basic characteristics of several 2D materials and the photodetection mechanisms, this paper reviews the research progress of silicon photonic integrated photodetectors based on 2D materials and summarizes existing device structure and performance. Finally, prospects for strategies to obtain high-performance silicon photonic integrated 2D material photodetectors and their commercial applicability are presented with considerations for large-scale 2D material integrations, device structure, and metal-semiconductor interface optimizations, as well as emerging 2D materials.
Research progress on coherent synthesis of optical frequency comb
MA Jun-chao, MENG Li-li, ZHANG Rui-xue, ZHUO Xiao, NI Kai, WU Guan-hao, SUN Dong
2021, 14(5): 1056-1068. doi: 10.37188/CO.2021-0071
Abstract:
Optical Frequency Comb (OFC) possesses unique time(frequency) domain characteristics such as narrow pulse width, high frequency precision, stable frequency comb teeth and well-defined optical coherence, etc. Therefore, it has become a hot research topic in various fields including ultra-fast laser technology and metrology science in recent years. Meanwhile, OFC has also been developed into an important scientific research instrument. Recently, a novel light source based on the coherent synthesis of OFCs has been developed, which can realize the periodical, high-speed (up to radio frequency) and stable modulation of the polarization or the orbital angular momentum of light. In this review, we try to introduce recent developments on the fundamental principles, experimental techniques and characterization methods of the novel light source based on the coherent synthesis of OFCs, starting from the basic concepts of OFC and mainly covering two aspects: polarization modulation and orbital angular momentum modulation respectively. We also try to provide some perspectives on the applications of OFC based on the coherent synthesis techniques in the fields of solid-state spectroscopy, optical manipulation and the interaction between light and matter, etc.
Progress of tunable micro-nano filtering structures
YU Xiao-chang, XU Ya-qing, CAI Jia-chen, YUAN Meng-qi, GAO Bo, YU Yi-ting
2021, 14(5): 1069-1088. doi: 10.37188/CO.2021-0044
Abstract:
Because of the large size and immobility working modes, traditional spectral imaging systems struggle to meet increasingly complex practical needs. Tunable micro-nano filtering structures show unique advantages for their lighter weight and greater flexibility, so they are promising candidates for achieving adaptive and intelligent operation in the future. This article summarizes a variety of tunable filtering methodologies and their operational principles both in domestic and foreign research within the last several years. It illustrates static tunable methods such as utilizing liquid crystal and phase-change materials, some dynamic tunable filtering structures such as Fabry-Pérot cavity, micro-nano tunable grating as well as some driving approaches like mechanical stretching, electrostatic driving, optical driving, etc. Meanwhile, this article also introduces some frontier researches based on microfluidic chips and graphene. In the end, it discusses the barriers, challenges and future trends of development for tunable micro-nano filtering structures.
Research progress of elastic emission machining in optical manufacturing
LI Jia-hui, HOU Xi, ZHANG Yun, WANG Jia, ZHONG Xian-yun
2021, 14(5): 1089-1103. doi: 10.37188/CO.2021-0022
Abstract:
The requirements of modern optical engineering in fields such as deep ultraviolet lithography, extreme ultraviolet lithography and advanced light sources drive the continuous development of advanced optical manufacturing technology. Modern optical engineering requires the surface roughness of ultra-smooth optical components to reach the atomic level and the surface shape profile error in the full spatial frequency to reach RMS(Root Mean Square) sub-nanometer or even a few dozen picometers. This drives the manufacturing requirements of ultra-smooth optical components to approach the processing limits. At present, there are still technical challenges to achieve the ultra-smooth polishing technology and equipment required for the above ultra-high precision needs. Atomic level ultra-smooth polishing of complex surfaces such as cylinders, ellipsoids and toroids is still a primary direction of research at both domestically and abroad. Elastic emission machining is an atomic-level ultra-smooth processing method with stable removal functionality and ultra-low subsurface defect creation, which can be used for manufacturing optical components with the above-mentioned accuracy requirements. We summarize the research progress of elastic emission machining and equipment at both domestically and abroad, the principles of elastic emission machining which contains fluid characteristics, the movement characteristics of polishing particles and chemical characteristics, the equipment of elastic emission machining, and the factors affecting the improvement of surface roughness and material removal rate of elastic emission machining. Then we analyze the problems faced by elastic emission machining and equipment and look forward to their prospects. It is expected that this paper will provide a reference for the further development and application of elastic emission machining.
Budget analysis of focus control in advanced lithography (I) -optical path
ZHONG Zhi-jian, LI Chen-yi, LI Shi-guang, GUO Lei, WEI Ya-yi
2021, 14(5): 1104-1119. doi: 10.37188/CO.2021-0033
Abstract:
As the technology node of large-scale integrated circuits continues to shrink, the focus control of the lithographic tools becomes particularly difficult. In order to ensure the exposure quality of wafers, it is necessary to quickly and accurately adjust the wafer in the Depth of Focus (DOF) to a degree as small as few dozen of nanometers. For this reason, people need to carefully analyze the various factors that cause defocusing or process window changes in the lithographic process, make a reasonable focus control budget, and control the various error factors within a certain range. This paper focuses on Extreme Ultraviolet (EUV) lithography, reviews the factors that affect focus control in the optical path of an advanced EUV lithographic tool and summarizes their principles, simulation and experimental results. It can provide a reference when conducting advanced lithography focus control budget research.
Research progress of tunable fiber light sources with wavelength near 1 μm
DANG Wen-jia, GAO Qi, LI Zhe, LI Gang
2021, 14(5): 1120-1132. doi: 10.37188/CO.2021-0125
Abstract:
Tunable fiber light sources with wavelength near 1 μm are widely used in optical fiber sensing, laser cooling, photochemical, spectroscopy and medical fields. They have thus become an area of focus in fiber light source research in recent years. The development history of fiber light sources with wavelength tuning ability is firstly summarized systematically. Then, their problems and possible solutions are analyzed. Finally, the future developments of tunable fiber light sources near 1 μm are prospected.
Research progress of optical chaos in semiconductor laser systems
KUANG Shang-qi, GUO Xiang-shuai, FENG Yu-ling, LI Bo-han, ZHANG Yi-ning, YU Ping, PANG Shuang
2021, 14(5): 1133-1145. doi: 10.37188/CO.2020-0216
Abstract:
Chaotic lasers are widely used in secure communication, lidar, optical detection and other applications due to their noise-like randomness, excellent anti-interference and other advantages. Moreover, as semiconductor lasers have small size, stable structure and other advantages, it has become one of the main lasers to produce optical chaos. However, the chaotic laser output from conventional optical feedback semiconductor lasers has the problems of narrow signal bandwidth and delay characteristics, which seriously affect their applications. With consideration for these problems, a comprehensive introduction to reduce the delay characteristics and optimize the chaotic laser bandwidth are reviewed based on recent literatures. This paper also summarizes the research progresses of chaotic secret communication, which is very important in the synchronization of chaotic lasers. The chaotic output of semiconductor lasers and the applications of chaotic lasers are also summarized, and then their development and potential future applications are discussed.
Review of augmented reality display technology
SHI Xiao-gang, XUE Zheng-hui, LI Hui-hui, WANG Bing-jie, LI Shuang-long
2021, 14(5): 1146-1161. doi: 10.37188/CO.2021-0032
Abstract:
Augmented reality (AR) display technology has developed rapidly in recent years, and has become a research hotspot and development focus of the global information technology industry. It has the potential to revolutionize the ways we perceive and interact with various digital information. Recent advances in micro-displays and optical technologies offer new development directions to further advance AR display technology. This review analyzes the optical requirements of human visual systems for AR head-mounted displays and compares them with current specifications of AR head-mounted displays to demonstrate their current levels of development and main challenge. The basic principles and parameters of various micro-displays and optical combiners in AR head-mounted displays are introduced to explain their advantages and practicability, and their development trends are summarized.
3D small-field surface imaging based on microscopic fringe projection profilometry:a review
WANG Yong-hong, ZHANG Qian, HU Yin, WANG Huan-qing
2021, 14(3): 447-457. doi: 10.37188/CO.2020-0199
Abstract:
Intelligent manufacturing has become more precise, miniaturized and integrated. Representative integrated circuit technology and its derived miniature sensors such as Micro-Electro-Mechanical System (MEMS) have become widely used. Therefore, it is important for intelligent manufacturing development to accurately obtain the surface morphology information of micro-devices and implement rapid detection of device surface defects. Fringe Projection Profilometry (FPP) based on structural light projection has the advantages of being non-contact, highly precise, highly efficient and having full-field measurement, which plays an important role in the field of precision measurement. Microscopic Fringe Projection Profilometry (MFPP) has been developed rapidly during recent decades. In recent years, MFPP has made great progress in many aspects, including its optical system structures, corresponding system calibration methods, phase extraction algorithms, and 3D coordinate reconstruction methods. In this paper, the structure and principle of a three-dimensional measurement system of microscopic fringe projection are reviewed, and the calibration problem of a small field-of-view system that is different from the traditional projection model is analyzed. After that, the development and improvement process of the micro-projection system structure is introduced, and the reflection in the measurment caused by the system structure and metal material is analyzed. On this basis, the prospects of the development of microscopic fringe projection of 3D measurement system are discussed.
Development progress of Fe2+:ZnSe lasers
XU Fei, PAN Qi-kun, CHEN Fei, ZHANG Kuo, YU De-yang, HE Yang, SUN Jun-jie
2021, 14(3): 458-469. doi: 10.37188/CO.2020-0180
Abstract:
Mid-infrared lasers with emission spectrums located in the 3~5 μm atmospheric window have a wide range of possible applications in medical treatment, industrial processing, atmospheric remote sensing, space communication, infrared countermeasures and other fields. Transition Metal (TM) doped Ⅱ~Ⅵ group sulfide crystals can be used as the gain medium to achieve mid-infrared laser output. Among them, Fe2 +:ZnSe lasers are advantageous for their high conversion efficiency, their wide tunable range in the mid-infrared band and their compact structure. They are one of the most effective ways of achieving a short pulse with high power and high energy in the mid-infrared band. With the development of material technology in recent years, Fe2 +:ZnSe lasers have begun developing rapidly and have become a heavily researched topic. This paper reviews the development of a TM2+:Ⅱ~Ⅵ laser represented by a Fe2 +:ZnSe laser. The preparation methods of a Fe2 +:ZnSe gain medium are introduced and analyzed. The pump sources and factors affecting the performance of Fe2 +:ZnSe lasers are discussed. The output characteristics of the Fe2 +:ZnSe laser are reviewed. The latest development of Fe2 +:ZnSe lasers in room temperature and ultrashort pulse directions is summarized and prospected. The possible future development direction of Fe2 +:ZnSe lasers is discussed.
Research progress on portable laser-induced breakdown spectroscopy
ZENG Qing-dong, YUAN Meng-tian, ZHU Zhi-heng, CHEN Guang-hui, WANG Jie, YU Hua-qing, GUO Lian-bo, LI Xiang-you
2021, 14(3): 470-486. doi: 10.37188/CO.2020-0093
Abstract:
As a new rapid element analysis technique, Laser-Induced Breakdown Spectroscopy (LIBS) has proven iteself to have great potential for applications in increasingly numerous industrial fields. However, due to harsh outdoor and industrial environments, newer and higher requirements are being demanded of the LIBS system, such as the size of its instruments and the ability to resist a harsh environment. The rapid development of new laser technology promotes instrumentation for LIBS, allowing it to gradually step outside the laboratory and into the industry, and allows the LIBS system to gradually move towards instrumentation, miniaturization and portability.In this paper, the development of a portable LIBS that was developed in recent years was reviewed. The application and latest research progress of different kinds of laser source (small lamp pumped solid-state laser, diode pump solid-state laser and micro laser, fiber laser) applied to the portable LIBS system were summarized and discussed, providing insight into both the fiber optic LIBS (FO-LIBS) and the handheld LIBS. In addition, the basic problems of current portable LIBS and the prospects of its future were proposed and discussed.
Research progress of the laser vibration measurement techniques for acoustic-to-seismic coupling landmine detection
LI Jin-hui, MA Hui, YANG Chen-ye, ZHANG Xiao-qing, LUO Xin-yu, WANG Chi
2021, 14(3): 487-502. doi: 10.37188/CO.2020-0134
Abstract:
Acoustic-to-seismic coupling landmine detection technology based on the unique mechanical characteristics of landmines and the acoustic-to-seismic coupling principle has broad application prospects in safe and effective detection of landmines. However, a significant amount of work must be done to study the practical landmine detection system. Among them, the acoustic coupled surface vibration signals are very weak and complicated, which has always been a challenging problem to detect such signals accurately and quickly. In this paper, the non-contact laser measurement techniques of surface vibrations based on the principle of the acoustic-to-seismic coupling landmine detection technology were reviewed, including laser Doppler interferometry, electronic speckle pattern interferometry and laser self-mixing interferometry, etc., and the application feasibility of electronic speckle-shearing pattern interferometry in acoustic-to-seismic coupling landmine detection was analyzed.
Research progress on the modulation properties of new electro-optic materials
LÜ Xiao-lei, ZHAO Ji-guang, DU Xiao-ping, SONG Yi-shuo, ZHANG Peng, ZHANG Jian-wei
2021, 14(3): 503-515. doi: 10.37188/CO.2020-0039
Abstract:
Polarization modulation technology based on electro-optic crystals is playing an increasingly important role in the field of three-dimensional laser imaging. Due to the low field of view and high half-wave voltage of LiNiO3 (LN) materials, it is difficult for traditional electro-optic modulation technology to further improve 3D imaging performance. As the preparation technology of perovskite-structured electro-optical materials becomes more mature, electro-optic modulation technology based on new materials will become an excellent means to create a breakthrough in the detection accuracy of laser 3D imaging. PMNT, PLZT and KTaxNb1-xO3 (KTN) three typical materials have excellent electro-optical properties and dielectric properties that might surpass the field of view and half-wave voltage limitation. However, their applications in electro-optic modulation has lead to difficulties such as a low modulation bandwidth for PMNT, poor transmission performance for PLZT, and low practical application bandwidth for KTN. Future research will focus on the practicality of this modulation technology. The electro-optic modulation performance can be improved by doping and the signal-to-noise ratio of the system can be optimized by establishing performance characterization models.
Orthogonal frequency division multiplexing modulation techniques in visible light communication
XU Xian-ying, YUE Dian-wu
2021, 14(3): 516-527. doi: 10.37188/CO.2020-0051
Abstract:
With its unique advantages, Visible Light Communication (VLC) can compensate for limitations in radio frequency communication, allowing it to become a recent avid topic of research. Orthogonal Frequency Division Multiplexing (OFDM) has been widely used in VLC due to its high rate of data transfer and frequency selective fading resistance. We compare the performance of several OFDM modulation techniques in VLC, including unipolar schemes, enhanced schemes and hybrid schemes based on discrete Fourier transformation, as well as optical OFDM systems based on Hartley transform and LED index modulation. We perform these comparisons in terms of energy efficiency, spectral efficiency, bit error rate, and algorithm complexity. The principles of some kinds of optical OFDM systems are firstly illustrated and their spectrum efficiencies are theoretically analyzed and compared. We also research and analysis the improved design of receivers in optical OFDM systems. The challenges and upcoming research of OFDM systems in VLC are summarized. The research in this paper can provide a research reference and propose more efficient unipolar modulation schemes to further improve the spectral efficiency and reliability of optical OFDM systems.
Research advances in adaptive interferometry for optical freeform surfaces
ZHANG Lei, WU Jin-ling, LIU Ren-hu, YU Ben-li
2021, 14(2): 227-244. doi: 10.37188/CO.2020-0126
Abstract:
Optical free-form surfaces are difficult to detect due to their rich degrees of freedom. Interference detection methods are both highly precise and non-contact. However, the static compensator in a traditional interferometer faces difficulty in achieving in-situ tests of unknown surface shapes or those changing during fabrication. Therefore, programmable adaptive compensators for large dynamic ranges have become a well-researched topic in recent years. Combined with the research work in the field of freeform surface metrology, we introduce the latest research progress in adaptive interferometry for optical freeform surfaces. Adaptive interferometers based on a Deformable Mirror (DM) or Liquid Crystal Spatial Light Modulator (LC-SLM) are analyzed in detail. An adaptive controlling algorithm in the adaptive interferometer is introduced as well. Finally, the advantages and development bottleneck of the above two kinds of adaptive interferometry are summarized and the prospects for the future development of freeform surface adaptive interferometers are proposed.
Interrogation technology for quasi-distributed optical fiber sensing systems based on microwave photonics
WU Ni-shan, XIA Li
2021, 14(2): 245-263. doi: 10.37188/CO.2020-0121
Abstract:
Quasi-distributed fiber sensing systems play an important role in the fields of civil engineering, energy surveying, aerospace, national defense, chemicals, etc. Interrogation technology for quasi-distributed fiber sensing systems based on microwave photonics is widely used in high-speed and high-precision signal demodulation and sensor positioning in optical fiber multiplexing systems. Compared to conventional optical wavelength interrogation, this technology greatly improves system demodulation rate and compensates for the defects of traditional sensor positioning methods. This paper introduces the recent research progress of quasi-distributed fiber sensing interrogation technology based on microwave photonics; compares and analyzes the advantages and disadvantages of several existing microwave demodulation systems from the perspective of their fiber grating quasi-distributed sensing and fiber Fabry-Perot quasi-distributed sensing systems, respectively; and provides a summary of the prospective direction of future research in quasi-distributed fiber sensing interrogation technology based on microwave photonics.
Research progress of 0.9 ~ 1.0 μm near-infrared continuous-wave fiber lasers
DANG Wen-jia, LI Zhe, LU Na, LI Yu-ting, ZHANG Lei, TIAN Xiao
2021, 14(2): 264-274. doi: 10.37188/CO.2020-0193
Abstract:
Near-infrared continuous-wave fiber lasers with wavelengths of 0.9~1.0 μm have important application prospects in the fields of high-power blue and ultraviolet laser generation, high-power single-mode pump sources, biomedicine and lidars. They have thus become a heavily researched topic in recent years. At present, their gain mechanisms mainly include a rare earth ion gain or a nonlinear effect gain. In this paper, the research progress of 0.9~1.0 μm fiber lasers based on these two kinds of gain mechanisms are reviewed in detail, and the technical bottlenecks and solutions of these lasers are analyzed. Furthermore, the potential directions for the future of their research are proposed.
Time-delay interferometry for space-based gravitational wave detection
WANG Deng-feng, YAO Xin, JIAO Zhong-ke, REN Shuai, LIU Xuan, ZHONG Xing-wang
2021, 14(2): 275-288. doi: 10.37188/CO.2020-0098
Abstract:
The Time-delay Interferometry (TDI) technique is of important value for China’s gravitational wave detection program and other space-based laser interferometry missions. In space-based gravitational wave detection, laser interferometry is utilized to achieve ten-picometer precision in the displacement measurements between drag-free proof masses. Laser frequency noise and clock frequency noise are the two dominant noises in the measurement. In the European LISA (Laser Interferometer Space Antenna) program for gravitational wave detection, TDI technique is used to remove laser noise and displacement noise of optical platform by time-delaying and linearly combining the twelve phase measurement data of the three satellites and thus creating an interferometer with equal-length beams. For the cancellation of clock noise, the frequencies of onboard clocks are multiplied to GHz levels and then the GHz clock signals are added on inter-satellite laser links by phase modulation. Finally, the clock noise can be extracted from the generated clock-sideband beat note, eliminating the clock noise terms in the TDI data combination. For the time-delay operation in the data post-processing of the TDI, there is also a requirement for the precise measurement of the absolute distances between three satellites. Therefore, in the TDI scheme, there are three functions applicable to the inter-satellite laser links: displacement measurement, clock sideband modulation and absolute distance ranging. The latter two functions consume the power of the optical carrier by 10% and 1%, respectively. The TDI demonstration in the LISA’s ground-based testbed shows the laser noise and clock noise can be suppressed by the factor of 109 and 5.8×104, respectively.
Development status and trend of micro-satellite laser communication systems
GAO Shi-Jie, WU Jia-Bin, LIU Yong-Kai, MA Shuang, NIU Yan-Jun, YANG Hui-sheng
2020, 13(6): 1171-1181. doi: 10.37188/CO.2020-0033
Abstract:
With its high speed, small size, light-weight and low power consumption, space laser communication has become an indispensable and effective means of high-speed communication between satellites, especially in micro-satellite applications, which can benefit more strongly from the advantages of laser communication. This paper provides a detailed introduction of the latest research progress in the field of micro-satellite laser communication technology. On this basis, key techniques such as light miniaturization of identical orbital terminals, light miniaturization of different orbital terminals and turbulence mitigation technologies are summarized, and the development trends of the technology’s applications, duplex communication, single-point to multi-point, localization and batch production capacity are concluded.
Review of laser speckle target detection technology
GAO Wei-ke, DU Xiao-ping, WANG Yang, YANG Bu-yi
2020, 13(6): 1182-1193. doi: 10.37188/CO.2020-0049
Abstract:
Target detection technology based on laser speckles is a kind of laser detection technology that has been ignored for a long time. In this technology, the laser speckle, which is regarded as noise in the traditional laser detection technology, is used as a new source of information. By analyzing the formation mechanism of a laser speckle pattern, the relationship between the statistical characteristics and the physical characteristics of the target is explored, and the effective analysis and inversion methods are combined to obtain the target’s shape, size, surface roughness and dynamic parameters. Compared with traditional laser detection technology, target detection technology based on laser speckles has a simple structure, has low optical system requirements, is sensitive to the physical and fretting characteristics of the target’s surface, and has been widely used in aerospace, medicine, industry, military and other fields. This paper classifies and summarizes the various kinds of speckle-based target detection technologies from recent years, compares and analyzes their applications, advantages and disadvantages, as well as the environmental restrictions. Finally, this paper prospects the trend for the future development of target detection methods based on laser speckles.
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