## 留言板

PVDF及其共聚物薄膜拥有极佳的电活性、较高的衍射效率、显著的非线性光学效应，广泛应用于光电转换、光调控、光开关等光电功能器件等领域。本文简要介绍了近年来PVDF及其共聚物薄膜非线性光学研究方面的主要进展，指出该类薄膜共混、纳米掺杂、超薄化的发展方向，同时需从第一性原理-光子带隙计算着手研究其非线性光学性质，以高灵敏度Z-扫描及马克条纹法结合椭偏为主要测量方式，为该类薄膜的非线性光学研究及制备提供一定的参考。

Oxide Vertical Cavity Surface Emitting Lasers(VCSELs) are widely used in high-speed optical communications. The reliability of VCSELs is a very important index which requiring a high lifetime and low failure rate in the application process. Understanding the root causes and mechanisms of VCSEL fails is necessary and helpful to improve device reliability. In this paper, we summarize and analyze the most common failure modes, causes and mechanisms observed in oxide VCSELs from three main aspects of design, manufacturing and application, and some appropriate measures and suggestions are applied to prevent or improve them. Moreover, the three dominating factors leading to the failure of VCSELs including oxide layer stress, ESD and humidity corrosion are introduced in more detail. This article can be used as a good VCSEL failure analysis library for chip development and production researchers. At finish, we will simply introduce the VCSEL failure cases encountered in the actual accelerated aging verification process for more references.

Averaged intensity and spectral shift of partially coherent chirped optical coherence vortex lattices (PCCOCVLs) in biological tissue turbulence are investigated, where optical lattice structures in monochromatic optical field and spectral rapid transitions in polychromatic optical field are stressed. It is found that the beam profile evolves from annular structure with vortex core into a periodic array of lobes with dark zone, and it finally present a Gaussian-like pattern in biological tissue. Although lattice parameter modulates beam profile, it cannot affect spectral behavior in biological tissue turbulence. The analysis of spectral shift also shows that a smaller distance is beneficial to spectral rapid transition, where the transverse coordinate decreases with an increase of chirp parameter and a decrease of pulse duration. The accumulated turbulences in a longer distance can suppress not only spectral transition, but spectral shift. The reduction of spectral shift is accompanied by a stronger biological tissue turbulence. The results have the application possibility in image recognition, medical device and noninvasive optical diagnose in biological tissue.

2022, 15(1): 1-13.   doi: 10.37188/CO.2021-0115
[摘要](526) [HTML全文](203) [PDF 3910KB](165)

2022, 15(1): 14-21.   doi: 10.37188/CO.2021-0061
[摘要](205) [HTML全文](40) [PDF 3682KB](50)

2022, 15(1): 22-33.   doi: 10.37188/CO.2021-0101
[摘要](271) [HTML全文](81) [PDF 4639KB](20)

2022, 15(1): 34-44.   doi: 10.37188/CO.2021-0114
[摘要](184) [HTML全文](83) [PDF 4156KB](21)

2022, 15(1): 45-55.   doi: 10.37188/CO.2021-0129
[摘要](80) [HTML全文](21) [PDF 4206KB](24)

2022, 15(1): 56-64.   doi: 10.37188/CO.2021-0117
[摘要](234) [HTML全文](76) [PDF 4310KB](17)

2022, 15(1): 65-71.   doi: 10.37188/CO.2021-0127
[摘要](154) [HTML全文](61) [PDF 3696KB](25)

2022, 15(1): 72-78.   doi: 10.37188/CO.2021-0116
[摘要](181) [HTML全文](62) [PDF 3955KB](34)

2022, 15(1): 79-89.   doi: 10.37188/CO.EN.2021-0009
[摘要](111) [HTML全文](39) [PDF 4821KB](21)

Dual-wavelength retinal imaging adaptive optics systems are suitable for high contrast and resolution imaging of retinal capillaries. The compensation of the Longitudinal Chromatic Aberrations (LCAs) in dual-wavelength adaptive systems is researched. The LCA is measured, the measured wavefronts are analyzed, and the arbitrary wavefront LCA compensation method is given. An adaptive correction experiment is carried out and the experimental results indicate that the root mean square error of the wavefront is reduced to 0.16 λ (λ=589 nm) and the retinal capillary resolution is improved to 6 μm. This work may be used for the clinical applications of retinal imaging.
2022, 15(1): 90-100.   doi: 10.37188/CO.EN.2021-0004
[摘要](193) [HTML全文](106) [PDF 3891KB](24)

As a testing method for large convex aspheric surface, the single optical wedge compensation test 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 tests. To address this, a method is developed to calibrate the system error of single optical wedge test paths using a Computer Generation Hologram (CGH). We first analysed the source of system error in the optical path of a 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 was designed for optical wedge compensators with a diameter of 150 mm. Based on the analysis results, the calibration accuracy of the CGH was 1.98 nm RMS, and after calibration the test accuracy of single wedge compensation was 3.43 nm RMS, 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 the test system errors of optical paths. Thus we address the problems affecting 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, were 0.023 and 0.011 λ RMS, respectively.
2022, 15(1): 101-110.   doi: 10.37188/CO.EN.2021-0006
[摘要](159) [HTML全文](70) [PDF 3662KB](16)

A high-sensitivity Surface Plasmon Resonance (SPR) sensor comprising of an eccentric core ten-fold Photonic Quasi-crystal Fiber (PQF) with a D-shaped structure and partially coated with Indium Tin Oxide (ITO) is designed and numerically analyzed. The eccentric core D-shaped structure makes the analysis of liquids more convenient and also strengthens the coupling between the core mode and Surface Plasmon  Polariton (SPP) mode to improve the sensing sensitivity. The characteristics of the sensor are investigated by the Finite Element Method (FEM). The wavelength sensitivity increases with increasing Refractive Indexes (RIs) and the maximum wavelength sensitivity and resolution are 60000 nm/RIU and 1.67×10−6 RIU, respectively. The sensor delivers excellent performance and has large potential applications in the measurement of liquid refractive indexes.
2022, 15(1): 111-118.   doi: 10.37188/CO.EN.2021-0001
[摘要](179) [HTML全文](98) [PDF 3754KB](20)

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. When the topological charge m is 2, the scintillation index of the vortex beam 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 m propagation distance, and the scintillation indices of both the vortex beam with m=2 and the Gaussian beam increase with the increase of the propagation distance.
2022, 15(1): 119-131.   doi: 10.37188/CO.2021-0092
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Owing to the strong penetrating ability in the atmosphere, 532 nm-wavelength green laser has wide applications including free-space optical communications and laser three-dimensional mapping. A spectral filter, with a half-power bandwidth of less than 100 pm, is an important optical element to suppress the interference of background light. Therefore, an ultra-narrow band-pass filter based on optical interference film is designed and fabricated in this paper. The high and low refractive index film are made of tantalum pentoxide (Ta2O5) and silicon dioxide (SiO2), respectively. The designed optical thin films are deposited on a fused quartz substrate by double-ion-beam sputtering deposition method. The transmission spectra of the filters are measured by a tunable laser and a power meter. The half-power bandwidths of the filters are (60±2) pm, and the transmittance reaches 62.6%.
2022, 15(1): 132-143.   doi: 10.37188/CO.2021-0058
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Helmholtz-Kohlrausch effect (H-K effect) describes the influence of color purity on the perceived brightness of a colored object. Quantum dots (QD) based backlights can enhance the color quality of Liquid Crystal Display (LCD) with improved perceived brightness due to the well-known H-K effect. However, the H-K effect of QD embedded TVs (also known as QLED TV) has not been fully demonstrated. In this paper, we investigated the H-K effect of QLED TVs 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 a 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, 86% for pure green, and 74%-88% for bright colorful images. Moreover, QLED TVs are strongly preferred over YAG-LED TVs even when both QLED TV and YAG-LED TV show the same perceived brightness. The results imply the bright future of QLED TVs toward healthly displays.
2022, 15(1): 144-160.   doi: 10.37188/CO.2021-0084
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The technology of enhancing fluorescence emission can increase the sensitivity of fluorescence detection and the brightness of Light Emitting Diodes (LEDs), and is of great significance in improving the performance of light-emitting devices. Since the metal structure has a good effect in enhancing the local field and fluorescence emission, and the flexible dielectric material has flexible bendability characteristics, on the basis of above, we propose a flexible structure composed of Metal-Dielectric-Metal (MDM) to enhance the fluorescence emission. The influence of the structure on the directional emission enhancement of quantum dots is systematically studied by using the finite difference time domain method. Theoretical calculations show that the local undulations and arcs of the flexible MDM structure can promote fluorescence enhancement and increase the quantum efficiency of the quantum dots located at the center of the structure by about 7 times. They can alao change the refractive index and thickness of the dielectric to achieve the tunability of the target wavelength. At the same time, the experimental results shows that the flexible MDM structure does have a positive effect on the fluorescence enhancement. This discovery is valuable for future display technologies and flexible light-emitting devices. It is of certain guiding significance for the development and application of high-efficiency flexible devices.

2022, 15(1): 1-13.   doi: 10.37188/CO.2021-0115

2021, 14(5): 1039-1055.   doi: 10.37188/CO.2021-0003

2021, 14(5): 1056-1068.   doi: 10.37188/CO.2021-0071

2021, 14(5): 1069-1088.   doi: 10.37188/CO.2021-0044

2021, 14(5): 1089-1103.   doi: 10.37188/CO.2021-0022

2021, 14(5): 1104-1119.   doi: 10.37188/CO.2021-0033

2021, 14(5): 1120-1132.   doi: 10.37188/CO.2021-0125

2021, 14(5): 1133-1145.   doi: 10.37188/CO.2020-0216

2021, 14(5): 1146-1161.   doi: 10.37188/CO.2021-0032

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

ISSN 2095-1531

CN 22-1400/O4

CODEN ZGHUC8