Owing to their advantages such as low loss, high process tolerance, manufacturing process compatible with CMOS processes and good mode field matching with single-mode optical fiber, silica-based planar light-wave circuits (PLC) have been widely used in optical communication, optical interconnections and integrated optics. In this paper, the recent progresses of the silica-based PLC devices and their applications are reviewed. Silica-based PLC devices including beam splitters, array waveguide gratings, variable optical attenuator and their integration devices are described, and future development trends are proposed.

Optogenetics is an interdisciplinary subject consisting of neuroscience, optics, semiconductor optoelectronics and biomedical science. Light can be used as a tool applied in genetics to provide more efficient and accurate regulation and new ideas for clinical treatments on psychiatric illnesses. The integrated implanted biological optrode is a multi-functional microprobe which integrates light stimulation and feedback signal recording, and it has important applications in optogenetic researches on living mammals. The paper first reviews the history of optogenetics. Then the development and classification of optrodes are analyzed in detail. The structure and performance of different optrodes are further compared and evaluated, such as electrical performance, noise signal, biocompatibility and reliability. Finally, the improvement and future trends of optrodes are discussed.

In order to solve the problem of high power consumption in wide range measurement of flow velocity caused by low temperature coefficient of resistance (TCR) of commonly used metal thermistors materials such as platinum, a flexible MEMS thermal flow sensor with low power consumption and wide range based on amorphous germanium (a-Ge) film thermistors was designed. The a-Ge thermistor material has high TCR coefficient (about -0.02/K) and room temperature resistivity (5Ω·m), which makes the sensor can achieve a wide range of flow velocity measurement under low working temperature difference and power consumption. The design structure, working principle, 3D finite element modeling and thermal-flow field simulation results of the flexible MEMS flow sensor are described. It uses four a-Ge thermistors in the cavity film of flexible polyimide substrate as self-heating heat source and temperature measuring element at the same time. These four a-Ge thermistors form a Wheatstone bridge, which combines the principles of heat loss and thermal temperature difference to achieve a wide range of flow velocity measurement and direction finding. The simulation shows that the constant current power supply of Wheatstone bridge only needs 120μA, so that the temperature difference between the working temperature of a-Ge thermistors and the ambient temperature is no more than 6K, the flow velocity in the range of 0~50m/s can be measured, and the power consumption is within 1.368mW. This flexible flow sensor is easy to be fabricated in batches by using MEMS technology and can be applied to curved surfaces, which is very suitable for low-power flow sensing fields such as the Internet of Things.

In responses to the requirements of low noise, high sensitivity and high bandwidth, a quad photodetector in space laser interferometry for detecting gravity waves is developed. The quad photodetector is a hybrid of quad photodetector chip and readout circuits, while the chip is made by four same InGaAs PIN photodiodes with double depletion regions, so as to lower the photodiode capacitance, narrow the gap between quadrants, and improve the detection sensitivity. The detection module integrated with photodetector chip and low-noise transimpedance amplification readout circuits was simulated by PSPICE. By optimizing the circuit parameters, the gain, bandwidth and noise power density were calculated. Test results show that the integrated detection module has a -3dB-bandwidth of 28.3MHz, and a noise power density of 1.7pW/Hz1/2, and the inconsistency between quadrants is 0.76%. Therefore, the quad photodetector can satisfy the basic requirements of space laser interferometry.

In this paper, a graphene M-Z electro-optical modulator based on S-Y branch SOI ridge waveguide was designed by COMSOL, and the influence of the Y-branch waveguide curvature radius, the length of the phase arm, core spacing and input-output straight waveguide length on the modulator were analyzed. On this basis, the performance index of the electro-optical modulator was calculated and optimized. Finally, a silicon graphene M-Z electro-optical modulator with a 3dB bandwidth of 143GHz and an extinction ratio of 15.05dB was designed.

Four-level pulse amplitude modulation (PAM4) plays a more and more important role in high-speed serial link systems and receives more and more attention. The traditional traveling wave Mach-Zehnder modulator (TWMZM) has a spectral ratio of 1∶1. In this paper, a traveling wave Mach-Zehnder modulator with asymmetric light intensity (AP-TWMZM) is proposed. Its optical power spectral ratio at the input side is 4∶1. The PAM4 optical signal is generated by the upper and lower arms modulation to realize the optical domain PAM4 modulation. Modeling and simulation with the Lumerical software shows that compared with traditional TWMZM, AP-TWMZM has higher modulation efficiency and its linearity is as high as 0.948.

According to the application requirements of small satellite, mirco-and-nano-satellite, in this paper, the chip structure and key technologies of CMOS image sensors with radiation tolerant technology were studied. And mainly the technologies of row and column circuit, low noise readout, programmable gain amplifier and on chip ADC were analyzed and simulated. Simulations were performed on the key circuits and the whole chip layout was verified based on 0.35μm CMOS radiation tolerant technology. Test results show that this sensor presents such characteristics as high dynamic range, low noise and radiation tolerance. The noise is 42e- and the dynamic range is 69dB. The noise matches the requirements when the total dose irradiation is over 100krad(Si).

Aiming at the needs of high time resolution imaging in low light environment, based on CIS process, a large-size PPD pixel device with ultra-fast charge transfer is designed and simulated, which owns a gradient-doped triangular shape and central floating diffusion region. The doping shape and gradient doping of the N-buried layer can enhance the gradient potential formed on the transmission path, thereby the transfer of the photo-generated charge from the N buried layer to the charge storage area will be accelerated. At the same time, by making the gradient doping of the transfer transistor channel, the rebound charge is reduced and the transfer efficiency is effectively improved. Simulation results show that the charge transfer time is 1ns and the rebound charge level is below 1e- when the triangular branch-shaped circular pixel device contains 30,000 charges and the charge transfer efficiency reaches 99.9%. Thus, the PPD pixel device can be used for high time resolution imaging in low light environment.

In response to the need for real-time temperature measurement inside the motor, a nested tube fiber grating sensor was designed. It uses a ceramic substrate as the inner structure, a 304 stainless steel tube as the outer protection, and a pure silica fiber grating written by a femtosecond laser as the temperature sensing element. An optical fiber sensing test system of constant temperature oil bath was built, and the temperature characteristics of the sensor were studied by the method of cycling temperature rise and fall. Test results show that the sensor presents good temperature measurement performance, and the linear correlation coefficient of the temperature rise and fall experiment is 0.9999. In the long-term cycle experiment, the wavelength repeatability reaches ±2pm, and the hysteresis error is less than 5pm. It has high reliability and can be used for temperature monitoring inside the motor.

The transmission process of LD pump light in the water cooling structure of side pump module is studied in this paper. Based on the influence of module structure parameters, light wave transmission characteristics and medium transmission characteristics, the polarization state change, light intensity attenuation process and change rules of pump light on the surface and inside of each medium are systematically analyzed. The attenuation of light intensity caused by the surface Fresnel effect and internal absorption effect is mainly analyzed. Finally, the loss coefficient and polarization state change matrix of the pump light in a single round trip in a water-cooled structure are calculated. The analysis results can be used for reference to optimize the pumping efficiency and enhance the heat dissipation effect of the module.

In order to realize the measurement of the multi-dimensional force of the joints of the robot wrist, a Maltese cross-type fiber grating multi-dimensional force sensor is designed in this paper. The sensor consists of two circular rings, four equal cross-section cantilever beams distributed at 90° between the two rings and a fiber grating pasted on them. The sensing principles of the sensor are analyzed and the mechanical simulation analysis of the sensor is performed by ANSYS. The strain of the cantilever beam under the force of different parts of the sensor is studied, an experimental platform is built to perform the calibration experiment of the sensor, and the temperature compensation is studied. By making mathematical analysis on the simulation and test results, the relationship between the central wavelength shift and the force on the sensor is obtained. Experimental results show that the sensor can accurately measure the size and position of the wrist force within the error of 1.6%. Owing to its strong anti-interference ability and good stability, the sensor can be used in complex environments.

The effects of well width, barrier height and strain on the refractive index of TE mode and TM mode of quantum well are analyzed and the physical mechanisms were dissected. The results show that for the polarization dependence of refractive index caused by quantum confinement effect of quantum well, the smaller the well width or the higher the barrier height, the larger the polarization dependence of refractive index. When the compressive strain increases, the polarization dependence of refractive index increases. Tensile strain can overcome the influence caused by quantum confinement effect, for quantum well structures with different well widths and barrier heights, there are suitable tensile strains to minimize the polarization dependence of refractive index. The smaller the well width or the higher the barrier height, the larger the tensile strain is required. Based on the above analysis, a design method is proposed to realize low polarization dependence of refractive index of quantum well and a quantum well In0.49Ga0.51As/In0.77Ga0.23As0.5P0.5 with low polarization dependence of refractive index (＜0.03) within C-band (1530~1565nm) is designed. The research result is helpful for the optimization design of some key devices in optical network.

In this study, micron diamond polycrystalline films were prepared on the ceramic substrate coated with titanium by microwave plasma chemical vapor deposition method, with the mixed gases of methane and hydrogen as the reactive gases. The chemical composition, microstructure and surface morphology of the films were analyzed by SEM, Raman spectroscopy and X-ray experiments. The field emission performance of the thin films was studied by the field emission instrument of the secondary structure and scanning tunneling microscope, and the results indicated that the emission point of the micron diamond polycrystalline film mainly originated from the polycrystalline particles. The emission properties of different areas on the surface of single polycrystalline particles were further studied, and it is found that the field emission property will be affected by various factors.

A series of CaSrSiO4 nanophosphors with different Tb3+-doped concentrations have been prepared by high-temperature solid-state reaction method. SEM image shows that the powder particles show a shape of ball and a diameter of about 30~50nm. XRD pattern of the samples doped Tb3+ ions is basically consistent with that of CaSrSiO4 matrix, indicating that Tb3+ dopant has little influence on the crystal structure of CaSrSiO4 powder. Under the 285nm excitation, the intense ultraviolet, blue and green PL spectra are observed and the optimum Tb3+-doped concentration is 0.7%. Finally, the CaSrSiO4∶0.3Tb3+ phosphor is annealed by CO2 laser and its spectral intensity is enhanced by more than 50%. At the same time, the effect of annealing process parameters on PL characteristics of CaSrSiO4∶Tb3+ phosphor is discussed.

Antimony doped tin oxide (ATO) films were deposited on glass substrate by magnetron sputtering using a ceramic target of 96at% SnO2/4at% Sb2O3. The effects of sputtering power, pressure and post annealing on the near-infrared (NIR) blocking property of ATO films were investigated. The Uv-Vis-NIR transmission spectra and Hall Effect were measured and the microstructure of the films was analyzed with XRD and SEM. It was demonstrated that the ATO films deposited at room temperature showed relatively high transmittance in NIR region, while after annealing in nitrogen, the ATO films deposited under different sputtering powers and pressures performed obvious decrease in NIR transmittance respectively. For ATO films deposited at a sputtering power of 200W with a pressure of 1.4Pa in 10% O2 atmosphere, the transmittance at 550nm increased from 80.9% to 85.8% and that at 1500nm decreased from 84.6% to 23.0% after annealing at 500℃ for 1 hour in nitrogen.

Friction-induced selective etching has advantages of low cost, simple operation, and low destruction, thus it is regarded as an important route to realize micro/nanofabrication on monocrystalline silicon surface. To investigate the mask effect of friction-induced mechanical scratch in micro/nanofabrication of silicon surface, the topography and height of line/area structures under mechanical scratch were studied in selective etching and compared with that under oxide layer. It was found that there was no significant difference in mask effect of mechanical scratch and oxide layer, and corresponding evolution mechanism of topography under two different masks was discussed. Finally, the fabrication of composite nano-patterns was achieved by combining mechanical scratch and oxide layer. The present study provides an important theoretical basis for the high-quality and controllable processing of silicon surface, which is based on friction-induced selective etching.

In this paper, the temperature and reaction source gas flow of growing α-Ga2O3 by hydride vapor phase epitaxy (HVPE) were optimized by numerical simulation. Different from the traditional reaction chamber in which Ga source carried by HCl or Cl2, we use the method of external Ga source, which can accurately adjust the component proportion, mole fraction and concentration of GaCl/GaCl3. In addition, the activation energy of the reaction between GaCl3 and O2 was calculated by molecular simulation software Gaussian, and the activation energy of α-Ga2O3 convert to β-Ga2O3 was obtained by fitting the experimental data. On this basis, we researched the growth temperature and the composition ratio of GaCl/GaCl3, and then we concluded the optimal growth conditions of HVPE α-Ga2O3.

Recently, rhenium disselenide (ReSe2) has become a research hotspot due to its good infrared light response and anisotropic properties. Through the salt-assisted chemical vapor deposition technology, large-area monolayer ReSe2 films with a size of 80 microns were successfully synthesized on SiO2/Si substrates. The morphology, spectrum, thickness and element composition of ReSe2 films samples were analyzed by means of Raman spectroscopy (Raman), photoluminescence spectroscopy (PL), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), revealing that the as-prepared ReSe2 films have high crystal quality. Field-effect transistor photodetectors were fabricated based on the monolayer ReSe2 films and their photoelectric properties were systematically investigated, and the response time of millisecond level is achieved.

Single image dehazing technology has made great progress, but the algorithm is complicated and the running time is long. For the purpose of hardware implementation, the dark channel priori algorithm is improved to reduce its time complexity and realize real-time dehazing. A dark channel map optimization method is proposed, which retains the edge information of the image, and eliminates the halo effect and the complicated operation of transmittance refinement. The method for estimating and adjusting atmospheric light, and a transmittance compensation method suitable for hardware implementation are proposed, which solves the problem of flicker between video frames and color distortion in bright areas such as the sky. The hardware implementation of the proposed algorithm is based on FPGA, and the results show that it can process video images with the resolution of 1920×1080 at the frame rate of 60f/s in real time, which is much better than that of the traditional dehazing algorithm.

In the signal sparse representation methods, the traditional sparse approximation based on transform basis cannot extract the texture features of image adaptively, and the sparse approximation algorithm based on the over-complete dictionary is too complex. To solve this problem, a sparse representation method based on sparse dictionary optimization of wavelet transform is proposed. Based on the wavelet transform of image, this algorithm constructs over-complete dictionaries, and makes use of the similar attributes in interior and exterior on the texture in wavelet transform of images in the same scene, and classifies the over-complete dictionary with grey correlation degree, which improves the effectiveness of sparse representation. The new algorithm is applied in image signal sparse representation and image sampling and reconstruction experiments based on compressive sensing theory. The results show that the new algorithm improves the peak signal to noise ratio (PSNR) and structural similarity (SSIM) of reconstructed images as a whole, and can shorten the time of image reconstruction effectively.

To meet the requirement of real-time control of micro-unmanned aerial vehicles, a light-weighted Yolo-V4 single-stage image detection algorithm was designed, and a real-time target recognition system was designed based on a monocular camera. The light-weighted algorithm compresses the backbone network from 73 layers to 16 layers by improving the resolution of the input network and the parameters of the convolutional layer. And then by simplifying the residual and cross-level structures, the problem of deep network gradient disappearance was revolved, and the gradient information duplication was reducing. Finally, the shallow and deep features of the network were streamlined and merged from bottom to top. The K-means clustering algorithm was used to train the light-weighted model to improve the parameters of the pre-selection box and improve the detection accuracy of the algorithm for specific targets. Test results show that the proposed algorithm can reach a prediction accuracy of 98% for a specific target, a recall rate of 92%, a mean average accuracy of 90.70%, a single image detection time of 7.8ms, and a video processing speed of 125.6f/s, which can meet the real-time application requirements of micro unmanned aerial vehicles.

The automatic focusing of the holographic reconstructed image of the micro-milling tool in the digital in-line holographic tool setting technology is the key technology for realizing high-precision automatic tool setting, and the focus evaluation function is the basis for discriminating image quality. In this paper, by comparing the performance of several commonly used focusing evaluation functions, the imaging characteristics of the tools in the digital holographic autofocus process and the applicable focusing evaluation method are discussed. Aiming at the problem of automatic focusing, a piecewise progressive search method is proposed, which divides the search process into two processes: coarse adjustment of large step and fine adjustment of small step, and piecewise search for the optimal solution. Then the performance of the proposed search method is compared with that of the classical simulated annealing algorithm and Levenberg-Marquardt algorithm. The experimental results show that the proposed piecewise progressive search method has better applicability, and the computer simulation experiment further verifies the effectiveness of the proposed method.

In order to meet the tracking accuracy requirements of the laser communication system, a fast steering mirror system is used as the core of fine tracking control, and a voice coil motor with large stroke, high resolution and high bandwidth is selected to drive the fast steering mirror, and the control method of voice coil motor is studied. Firstly, the composition and working principle of the fast steering mirror system is analyzed. Then, modeling analysis is performed according to the equivalent circuit model of the voice coil motor, and the transfer function model of the fast reflector is obtained. Finally, the design principle of the analog controller, the proportional-integral-derivative (PID) circuit, the position detection circuit and the power amplifier circuit are introduced. The experimental results show that the angular resolution of the fast steering mirror is 1μrad, the repeated positioning accuracy is 3μrad, and the closed-loop bandwidth (-3dB) is 300Hz@1mrad, which can meet the requirements of laser communication system for stability, reliability, high precision, and strong anti-interference ability.

fast successive cancellation list flip (FSCLF) decoding algorithm is proposed to improve the problem that the decoding performance and complexity of the existing successive cancellation list flip (SCLF) decoding algorithm cannot be considered at the same time. The proposed algorithm speeds up the decoding by adding the identification of four special nodes. In the meantime, the construction of the critical set (CS) no longer depends on the error propagation caused by the previous decoding errors, instead, the log-likelihood ratio (LLR) value is calculated to determine the flipping position by the two special nodes of the R1 node and single-parity-check (SPC) node, and the information bit corresponding to the least reliable input LLR only need to be flipped when the parity check bit isn’t satisfied, thus both the number of the flipping and the complexity is reduced. Simulation results show that the signal-to-noise ratio of the FSCLF algorithm, compared with the SCLF algorithm, is improved about 0.09dB at the block error ratio (BLER) of 10-5. Therefore, the proposed decoding algorithm can play an important role in the middle and short code-length.