## 留言板

With the development of underwater optical communication, it is very important to study the propagation characteristics of light beams in ocean turbulence. In order to get closer to the actual situation, we build a device which can control both the salinity and the intensity of underwater turbulence to study the propagation characteristics of vortex beams and a Gaussian beam in underwater turbulence. The results show that compared with the underwater turbulence without sea salt, the light spot will be more diffuse and the light intensity will be weaker in the underwater turbulence with sea salt. The scintillation index of the vortex beam with topological charge m=2 in the underwater turbulence with salinity of 4.35‰ is larger than that in the underwater turbulence with salinity of 2.42‰, no matter it is strong turbulence or weak turbulence. When the vortex beam with m=2 propagates to the same distance, the scintillation index increases with the increment of the salinity and the intensity of underwater turbulence. Under different salinity conditions, the radial scintillation index of the vortex beam with m=2 decreases firstly and then increases with the increase of the radial distance. In addition, we set up another experimental device which can transmit a longer distance. The scintillation index of the vortex beam with m=2 is much higher than that of the Gaussian beam in the underwater turbulence within 20 meters, and the scintillation indices of both the vortex beam with m=2 and the Gaussian beam increase with the increase of the propagation distance.

Helmholtz-Kohlrausch effect (H-K effect) described the influence of color purity on the perceived brightness of a color object. Quantum dots (QD) based backlights can enhance the color quality of liquid crystal display (LCD) display with improved perceived brightness due to the well-known H-K effect. However, the H-K effect of QD embedded TV (also known as QLED TV) has not been fully demonstrated. In this paper, we investigated the H-K effect of QLED TV through a comparative study between QLED backlights and YAG-LED backlights. By comparing the viewers’ experimental results with the Kaiser and Nayatani model, we demonstrate that QLED TV shows significant H-K effect. To achieve the same perceived brightness with YAG-LED TV, the physical brightness of QLED TV was greatly decreased to 75% for pure red color, 86% for pure green color, and 74-88% for bright colorful images. Moreover, QLED TV is much preferred than the YAG-LED TV even when both QLED TV and YAG-LED TV show the same perceived brightness. The results imply the bright future of QLED TV toward health display.

Optical properties of periodic double-well potential are one of the frontier research fields in laser physics and quantum optics. In this work, we have employed time-periodic double-well potential for the investigation of Fano-type resonant tunneling of photon-assisted Dirac electrons in a graphene system. Using a double quantum well structure, it is found that the resonant tunneling of electrons in a thin barrier between the two quantum wells splits the bound state energy levels, and the Fano-type resonance spectrum splits into two asymmetric resonance peaks. The shape of Fano peak is regulated by changing the phase, frequency, and amplitude, that can directly modulate the electronic transport properties of Dirac in graphene. Our numerical analysis shows that the relative phase of two oscillating fields can adjust the shape of the asymmetric Fano type resonance peak. When the relative phase increases from 0 to \begin{document}$\pi$\end{document}, the resonance peak valley moves from one side of the peak to the other. In addition, the asymmetric resonance peak becomes symmetric at critical phase \begin{document}${{3\pi }/{11}}$\end{document}. Furthermore, the distribution of Fano peaks can be modulated by varying the frequency and amplitude of oscillating field and the structure of the static potential well. Finally, we suggest that these interesting physical properties can be used for the modulation of Dirac electron transport properties in graphene.

The single wedge compensation test method, as a testing method for large convex aspheric surface, has good applicability, robustness, and flexibility. However, various errors are coupled with one another during the test process and these errors are difficult to decouple; this affects the accuracy and reliability of the test process. To address this, a method is developed to calibrate the system error of single optical wedge test path using computer generation hologram (CGH). This study first analysed the source of the system error in the optical path of single optical wedge compensation test as well as the feasibility of using CGH for the calibration of an optical wedge compensation test system. In combination with engineering examples, a CGH is designed for optical wedge compensators with a diameter of 150 mm. Based on the analysis results, the calibration accuracy of the CGH is 1.98 nm RMS, and after calibration the test accuracy of single wedge compensation is 3.43 nmRMS, thereby meeting the high-precision test requirements of large convex aspheric mirrors. This shows that CGH can accurately calibrate the pose of single optical wedge compensators and test system errors of optical paths, address the problem of error decoupling in test optical paths, and improve the accuracy and reliability of the single optical wedge compensation method. Meanwhile, using CGH calibration, the system errors of the test optical paths, Tap#2 and Tap#3, are 0.023 and 0.011 λ RMS, respectively.

目的  为了对作物进行更灵敏、高效的生长监测，国内外相继设计了各类高光谱分辨率的光谱仪用来探测叶绿素荧光效率。本文对传统Offner光谱仪系统进行改进，得到了更高光谱分辨率的整体结构。  方法  选用了双反望远系统，光谱仪部分采用高刻线密度反射型凸面光栅，实现更高的光谱分辨率的光谱仪，在此基础上再添加放大透镜以满足长狭缝需求，同时得到了一种狭缝-像面在光栅同一侧的Offner结构。利用codev软件对望远系统和光谱仪部分的初始结构进行优化。  结果  结果表明，工作在670 nm~780 nm波段范围内时，光谱分辨率0.3 nm，在截止频率17 lp/mm下整体调制传递函数MTF>0.75，各视场条件下弥散斑均方根半径RMS<15 μm。  结论  可满足作物生长的叶绿素监测领域的高精度、实时性要求。

目的  在“太极计划”中，由卫星抖动引起的激光抖动噪声是影响激光干涉测量精度的主要噪声源之一，为保证测量精度，需抑制该噪声至10 nrad/√Hz@10 mHz。  方法  首先，采用由四象限光电探测器和相位计组成的角度敏感器进行角度信号测量，并利用马赫-曾德干涉仪结合比例-积分-微分控制技术，搭建了地基激光抖动噪声抑制系统。其次，分析了系统反馈控制能力以及系统对于抑制激光抖动噪声的有效性。  结果  实验结果表明：该系统可有效抑制激光抖动噪声，使得激光抖动噪声<4 nrad/√Hz@10 mHz。  结论  实验推进了“太极计划”对激光抖动噪声抑制水平的研究，为激光干涉测量奠定了物理实验基础。

目的  为了实现外周血有核红细胞的分离与释放，开发安全有效的非侵入式技术分离有核红细胞用于产前胎儿疾病诊断，以水凝胶材料为基底建立自动化细胞涂片制备系统，并构建用于识别释放有核红细胞的激光会聚和显微成像系统。  方法  首先，设计了细胞涂片制备机的机械结构，基于单片机制作上位机控制软件，优化推片角度和速度参数制备水凝胶膜基底涂片，在温敏水凝胶明胶中引入二维材料MXene，结合MXene的近红外光热转换特性，在水凝胶膜表面实现近红外光响应。然后在水凝胶基底膜表面进行全血推片实验，优化血液推片参数，制备得到单层细胞涂片。最后，建立激光会聚和显微成像光路，对有核红细胞进行识别定位后，808 nm激光器的光源经过准直镜和会聚镜聚焦到细胞涂片表面，产生光热效应进行细胞释放。  结果  实现了单层细胞涂片的加工制备，在808 nm近红外光下产生光热效应，经过激光会聚系统的调控，最终得到了光斑直径为300 μm的细胞定点释放区域。  结论  本文将自动推片技术应用于以水凝胶膜为基底的单层细胞涂片的制备，建立激光会聚与显微成像光路，通过水凝胶膜的近红外响应以及热响应特性，实现了有核红细胞的识别与定点释放，提高了有核红细胞分离富集的效率，在产前筛选诊断领域中具备广阔的应用前景。

目的   大视场生物成像分析仪能够满足稀有细胞和痕量病原微生物等待测样本量大，目标物稀少的情况下进行快速和准确检测的需求，在生命科学、食品药品检测、环境安全等领域中，有极其重要的作用。   方法   显微物镜以同轴三反成像理论为基础，采用视场离轴的方式设计，采用光学仿真分析，该系统光谱范围350−1100 nm、放大倍数β=−1，视场范围为150 mm×20 mm，数值孔径0.1，点列图直径的均方根小于3.5 μm，在空间截止频率178 lp/mm处，全视场的MTF均值大于0.35，畸变为0。   结果   实验结果表明：成像系统视场大、分辨率高，大视场生物成像分析仪系统检出率为98%。   结论   设计的离轴三反显微物镜成像质量良好，可满足应用需求。

目的  为了实现穿刺过程中的精准定位，设计研制了一款视场角为90°，焦距为0.67 mm的高分辨率可视穿刺针光学系统。  方法  为使光学系统的光轴垂直于穿刺针的倾斜刃面，利用反射棱镜对光束进行转折，实现45°视向角。光学系统采用反远结构，并对初始结构参数计算公式进行推导。优化设计后，系统成像质量接近衍射极限，最大光学元件尺寸小于1.5 mm。  结果  利用研制的光学系统和微型CMOS图像传感器，装配完成了一款直径4 mm的可视穿刺针。  结论  对该可视穿刺针分别进行调制传递函数(MTF)测试和成像试验，测试结果表明，研制的光学系统具有较好的成像质量，物方分辨率优于18.03 lp/mm，能够实现清晰成像。

Compared with the commonly used simulation algorithms such as finite element method (FEM) and finite-difference time-domain (FDTD) method, the boundary element method (BEM) has the advantages of high accuracy, small memory consumption, and ability to deal with complex structures. In this paper, the basic principle of three-dimensional BEM is given, the corresponding program based on C++ language is written, and the surface plasmon resonance (SPR) characteristics of a graphene nano-disk structure are studied. The scattering cross-section (SCS) spectral lines of a graphene nano-disk under different chemical potentials, as well as the distributions of electromagnetic fields at the resonance wavelengths are calculated. The electromagnetic response of the graphene nano-disk in the infrared band is analyzed. In addition, considering the common corrugations of graphene materials caused by defects during processing, we study the influence of the geometric parameters of a convex structure in the center of the graphene nano-disk on the resonance intensity, wavelength and field distributions. A spring oscillator model of charge movement is used to explain the simulation results.

2021, 14(4): 717-735.   doi: 10.37188/CO.2021-0030
[摘要](126) [HTML全文](43) [PDF 3209KB](38)

2021, 14(4): 736-753.   doi: 10.37188/CO.2021-0095
[摘要](67) [HTML全文](26) [PDF 15001KB](21)

Exploring topological phases of matter and their exotic physics appeared as a rapidly growing field of study in solid-state electron systems in the past decade. In recent years, there has been a trend on the emulation of topological insulators/semimetals in many other systems, including ultracold quantum gases, trapped ions, photonic, acoustic, mechanical, and electrical circuit systems. Among these platforms, topological circuits made of simple capacitive and inductive circuit elements emerged as a very competitive platform because of its highly controllable degrees of freedom, lowercost, easy implementation, and great flexibility for integration. Owing to the unique advantages of electrical circuits such as arbitrary engineering of long-range hopping, convenient realization of nonlinear, nonreciprocal, and gain effects, highly flexible measurement, many of the nonlinear, non-abelian, and non-Hermitian physics can be potentially realized and investigated using the electrical circuit platform. In this review, we provide the first short overview of the main achievements of topological circuits developed in the past six years, primarily focusing on their theoretical modeling, circuit construction, experimental characterization, and their distinction from their counterparts in quantum electronics and photonics. The scope of this review covers a wide variety of topological circuits, including Hermitian topological circuits hosting nontrivial edge state, higher-order corner state, Weyl particles; higher dimensional topological circuits exhibiting nodal link and nodal knot states; non-Hermitian topological circuits showing skin effects, gain and loss induced nontrivial edge state; self-induced topological edge state in nonlinear topological circuit; topological circuit having non-Abelian gauge potential.

2021, 14(4): 754-763.   doi: 10.37188/CO.2021-0035
[摘要](171) [HTML全文](49) [PDF 2117KB](39)

2021, 14(4): 782-791.   doi: 10.37188/CO.2021-0098
[摘要](93) [HTML全文](35) [PDF 5029KB](18)

Surface waves supported by structured metallic surfaces, i.e.metasurfaces, have drawn wide attention recently.They are promising for various applications ranging from integrated photonic circuits to imaging and bio-sensing in various frequency regimes. In this work, we show that surface states with diverse polarization configurations can be supported by a metasurface consisting of a single layer of bianisotropic metamaterial elements.The structure possesses D2d symmetry, which includes mirror symmetry in the xz and yz plane, and C2 rotational symmetry along y = ±x axis. Due to this unique symmetry, the metasuface supports both transverse electric (TE) and transverse magnetic (TM) waves along kx and ky directions, while a purely longitudinal mode and an elliptically polarized transverse electromagnetic(TEM) mode along ky = ±kx directions. The versatility of the surface modes on the metasurface may lead to new surface wave phenomena and device applications.
2021, 14(4): 792-811.   doi: 10.37188/CO.2021-0066
[摘要](244) [HTML全文](69) [PDF 3457KB](113)

In the last two decades, optical vortices carried by twisted light wavefronts have attracted a great deal of interest, providing not only new physical insights into light-matter interactions, but also a transformative platform for boosting optical information capacity. Meanwhile, advances in nanoscience and nanotechnology lead to the emerging field of nanophotonics, offering an unprecedented level of light manipulation via nanostructured materials and devices. Many exciting ideas and concepts come up when optical vortices meet nanophotonic devices. Here, we provide a minireview on recent achievements made in nanophotonics for the generation and detection of optical vortices and some of their applications.

2021, 14(4): 812-822.   doi: 10.37188/CO.2021-0023
[摘要](209) [HTML全文](38) [PDF 4757KB](47)

2021, 14(4): 823-830.   doi: 10.37188/CO.2021-0102
[摘要](98) [HTML全文](20) [PDF 3510KB](14)

2021, 14(4): 831-850.   doi: 10.37188/CO.2021-0014
[摘要](153) [HTML全文](80) [PDF 3928KB](50)

2021, 14(4): 851-866.   doi: 10.37188/CO.2021-0069
[摘要](72) [HTML全文](22) [PDF 4678KB](16)

2021, 14(4): 867-885.   doi: 10.37188/CO.2021-0036
[摘要](108) [HTML全文](58) [PDF 6720KB](36)

2021, 14(4): 886-899.   doi: 10.37188/CO.2021-0017
[摘要](161) [HTML全文](126) [PDF 4083KB](51)

2021, 14(4): 900-926.   doi: 10.37188/CO.2021-0108
[摘要](82) [HTML全文](37) [PDF 6900KB](16)

2021, 14(4): 927-934.   doi: 10.37188/CO.2021-0097
[摘要](65) [HTML全文](25) [PDF 4700KB](19)

Based on the spin Hall effect of photons, a metasurface can be used to generate and control light beams. In this paper, by means of one-dimensional chains of nanohole, a metasurface with rotational symmetry is designed. The Bessel beam can be produced by the spin Hall effect of Left-handed Circularly Polarized (LCP) and Right-handed Circularly Polarized (RCP) light simultaneously. Through the excitation of linearly polarized light, we can dynamically control the intensity and polarization of Bessel beam by controlling the coherent interference between two circularly polarized light excitation beams. At the same time, this method has the advantage of broadband modulation range.

2021, 14(4): 935-954.   doi: 10.37188/CO.2021-0076
[摘要](116) [HTML全文](36) [PDF 12268KB](31)

2021, 14(4): 955-967.   doi: 10.37188/CO.2021-0074
[摘要](173) [HTML全文](29) [PDF 7875KB](45)

2021, 14(4): 968-985.   doi: 10.37188/CO.2021-0080
[摘要](147) [HTML全文](40) [PDF 4580KB](54)

2021, 14(4): 986-997.   doi: 10.37188/CO.2021-0110
[摘要](174) [HTML全文](38) [PDF 3907KB](71)

2021, 14(4): 998-1018.   doi: 10.37188/CO.2021-0093
[摘要](125) [HTML全文](26) [PDF 5029KB](44)

2021, 14(4): 1019-1028.   doi: 10.37188/CO.2020-0171
[摘要](303) [HTML全文](92) [PDF 4031KB](25)

2021, 14(4): 1029-1037.   doi: 10.37188/CO.2021-0100
[摘要](60) [HTML全文](22) [PDF 8007KB](15)

2021, 14(3): 447-457.   doi: 10.37188/CO.2020-0199

2021, 14(3): 458-469.   doi: 10.37188/CO.2020-0180

2021, 14(3): 470-486.   doi: 10.37188/CO.2020-0093

2021, 14(3): 487-502.   doi: 10.37188/CO.2020-0134

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.

2021, 14(3): 503-515.   doi: 10.37188/CO.2020-0039

2021, 14(3): 516-527.   doi: 10.37188/CO.2020-0051

2021, 14(2): 227-244.   doi: 10.37188/CO.2020-0126

2021, 14(2): 245-263.   doi: 10.37188/CO.2020-0121

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.

2021, 14(2): 264-274.   doi: 10.37188/CO.2020-0193

2021, 14(2): 275-288.   doi: 10.37188/CO.2020-0098

2020, 13(6): 1171-1181.   doi: 10.37188/CO.2020-0033

2020, 13(6): 1182-1193.   doi: 10.37188/CO.2020-0049

2020, 13(6): 1194-1208.   doi: 10.37188/CO.2020-0032

2020, 13(6): 1209-1223.   doi: 10.37188/CO.2020-0131

2020, 13(6): 1224-1238.   doi: 10.37188/CO.2020-0237

2020, 13(5): 899-918.   doi: 10.37188/CO.2020-0035

2020, 13(5): 919-935.   doi: 10.37188/CO.2020-0037

2020, 13(5): 936-964.   doi: 10.37188/CO.2020-0010

2020, 13(4): 647-659.   doi: 10.37188/CO.2019-0241

2020, 13(4): 660-675.   doi: 10.37188/CO.2019-0231

ISSN 2095-1531

CN 22-1400/O4

CODEN ZGHUC8