Airglow is an important photochemical phenomenon in the mesosphere and lower thermosphere region (MLT region), and O2 A-band (762 nm) airglow is one of the best observation targets for temperature detection in the MLT region. The radiance data of O2 A-band night airglow observed by the Optical Spectrograph and InfraRed Imaging System (OSIRIS) in 2008 were used to study the global spatial and temporal distribution of the night airglow. For the altitude-quarter distribution of night airglow radiance in different latitudes, the results indicated that the highest radiance of O2 A-band night airglow existed near the altitude of 95 km. In contrast, the seasonal variations of O2 A-band night airglow in the Northern Hemisphere and the Southern Hemisphere were opposite. To be specific, the highest radiance appeared in the second and third quarters in the Northern Hemisphere but in the first and fourth quarters in the Southern Hemisphere. The latitude-longitude distribution of night airglow radiance in different quarters shows that the longitudinal distribution of O2 A-band night airglow is relatively uniform, while the latitudinal distribution fluctuates widely. The latitude region of the highest radiance varies in different quarters. The above results are consistent with those in the relevant literature, which prove the correctness of our results. Furthermore, the analysis of the seasonal variation law of airglow and its influencing factors reveals that the distribution of night airglow has an annual reciprocating trend. The spatial and temporal distributions of O2 A-band night airglow are of great significance for further research on instrument design.

In order to promote the application of MERSI II data in the ocean, this paper uses the visible infrared optical imaging remote sensing instrument (VIIRS), which is one of the mainstream sensors for water color remote sensing, as a reference, from the signal-to-noise ratio (SNR) and other aspects to conducte a preliminary assessment of the MERSI II data quality. The results show that the SNR values of MERSI II are higher than 300 in the visible band, and the maximum can reach 900, which meet the water bodies monitoring requirements. The SNR values of MERSI II are slightly lower than that of VIIRS in the visible band and the near-infrared band, and are not much different from VIIRS in the short-wave infrared band. In addition, the radiance calibrated MERSI II reflectance data at the top-of-atmosphere is in good agreement with the VIIRS data, the determination coefficients (R2) are higher than 0.5, and the blue band R2 can reach more than 0.9. The mean absolute percentage error (EMAPE) is less than 30%. The R2 in the 670-865 nm band of the Western Pacific is about 0.5, and the EMAPE is 5%-15%. The R2 can reach 0.8 in the 670-865 nm band of China’s coastal waters, and the EMAPE is 7%-24%. After a simple linear fitting, the MERSI II reflectance data at the top-of-atmosphere is closer to the VIIRS data. The EMAPE in the visible band drops to 8%, and the blue band drops to 3%. The above results show that the quality of MERSI II data is comparable to VIIRS and can be used for ocean remote sensing applications.

In order to improve the measurement accuracy of a phase grating position measurement system, it is necessary to reduce the diffraction efficiency of diffraction signals of the zero order and even diffraction orders, and enhance the diffraction efficiency of high odd order diffraction signals. At present, the known diffraction efficiency model of enhanced phase gratings restricts the range of values of the structural parameters. A special high odd order diffraction signal is used as the optimized target in the design. Therefore, in order to design the phase grating structure with diffraction enhancement and zero and even order diffraction missing for multiple high odd order diffraction signals, the diffraction efficiency of the enhanced phase grating is deeply studied. In this work, based on the scalar diffraction theory, the theoretical models of the phase grating structure and diffraction efficiency are established; the influences of grating structure parameters such as groove depth, grating ridge width, and grating ridge position on diffraction efficiency are analyzed. According to the constraints of phase grating position measurement system, the enhanced grating structure with multiple odd diffraction orders is obtained. This kind of structure not only makes the zero and even order diffraction missing, but also improves the diffraction efficiency of the 5 th, 7 th, and 9 th order diffraction. This study is helpful to understand the diffraction principle of the enhanced phase grating and provides support for grating design.

For the diffractive optical elements (DOEs) in imaging optical systems, a range of incident angles is the normal working situation, and the introduction of antireflection coatings (ARCs) to DOEs affects polychromatic integral diffraction efficiency (PIDE). Relying on the phase function of DOEs, we modify the microstructure heights with ARCs in this paper. Furthermore, we build theoretical models of the relationship between the comprehensive PIDE and modified microstructure heights of single-layer and multilayer DOEs working within a certain incident angle range. With DOEs working in the infrared waveband as an example, we comparatively analyze the diffraction efficiency and PIDE with ARCs designed by the common method (CM) of maximizing the PIDE to obtain microstructure heights and by the proposed modified method (MM) based on modified microstructure heights. The simulation and calculation results show that both the change in incident angles and optical thicknesses of ARCs will induce the decline in the PIDE of DOEs with ARCs. With the MM, the comprehensive PIDE is 95.528% and 99.449%, respectively for single layer DOEs with a substrate of ZnSe working in the incident angle range of 0°-30° and multilayer DOEs in the 0°-20° range. This method provides a reference for the optimal design of DOEs.

Orbital angular momentum (OAM), as a new communication multiplexing dimension, has a wide range of applications in the fields of atmospheric laser communication and satellite communication. Here, dual-channel multiband OAM modulation is explored as a means of information transmission. Two-channel multiband signals are used to generate vortex beams with different topological charge values for coherent superposition to produce different light intensity patterns. These patterns are recorded by a charge-coupled device (CCD) camera at the receiving end, where differences in light intensity information denote differences in symbol information. When dual-channel quaternary information is transmitted, 16 different light intensity patterns can be generated. To ensure the differences among light intensity patterns, a coding scheme based on light intensity correlation is proposed. The effect of atmospheric turbulence on light intensity pattern recognition is then explored. The use of a convolutional neural network (CNN) for light intensity information recognition is found to significantly improve the recognition rate of light intensity information under the influence of atmospheric turbulence.

In current quadrature phase shift keying (QPSK) systems for coherent optical communications, there are two algorithms based on complex operation and angle operation to recover carrier phase. This paper analyzed and compared the recovery performance and implementation complexity of the Viterbi-Viterbi phase estimation (VVPE) algorithm based on complex operation and the barycenter phase estimation (BCPE) algorithm based on angle operation. The simulation proves that the VVPE algorithm is stronger in resisting additive noise than the BCPE algorithm and has a lower probability of cycle slip. The performances of the two algorithms are close when there is no cycle slip. In this paper, we carried out QPSK coherent reception experiments with rates of 2.5 GBaud (the product of symbol rate and linewidth is 4×10 -5) and 10 GBaud (the product of symbol rate and linewidth is 1×10 -5). Then, we evaluated the performance of the two algorithms using the offline Matlab and Verilog methods. For the 2.5 GBaud QPSK signal, after the length of the average filter is optimized, the receiving sensitivity of the two algorithms is -52 dBm@1×10 -3, and when the cycle slip occurs, the receiving power of the VVPE algorithm and BCPE algorithm is -54 dBm and -53 dBm, respectively. For the 10 GBaud QPSK signal, after the length of the average filter is optimized, the receiving sensitivity of the two algorithms is -47 dBm@1×10 -3, and in the case of cycle slip, the receiving power of the BCPE algorithm is -52 dBm. Relying on Xilinx Virtex Ultrascale+ FPGA, this paper compared the two algorithms with 10 GBaud system rate and 64 parallel channels. Regarding 8-bit and 16-bit input signals respectively for the VVPE algorithm and BCPE algorithm, the receiving sensitivity is -51 dBm@2×10 -2. The occupancy of the hardware look-up table of the BCPE algorithm is about 5.78% lower than that of the VVPE algorithm.

According to the approximate calculation theory of the amplitude distribution of coherent optical imaging, the imaging system is a linear space invariant system, and the transfer function of the ocular circle is defined as the filter of the geometrical optical image spectrum. Using the theory for accurately calculating the amplitude and phase distributions of image optical field, we found that the imaging system was no longer a linear space invariant system and that the physical definition of the transfer function needed to be modified. Through simulation and optical experiments of single lens coherent optical imaging and digital holography imaging, we verified the new definition of the transfer function as a spatial filter for geometric optical images diffracted by Fresnel lenses at a specific distance.

The traditional two-dimensional JND (Just Noticeable Difference) model can only estimate the minimum noticeable difference of the planar image, and is not completely suitable for the large field of view image under virtual stereo vision. First, according to the visual characteristics of the human eye, corresponding binocular observation experiments are designed for the four masking characteristics of brightness, contrast, fovea and stereo depth, and the mathematical model of JND is established through experimental data, and compared with other current JND models. The results show that this model can remove more visual redundancy under the same perceptual quality. Then the visual perception redundancy model is applied to image compression. For this purpose, a multi-level compression algorithm is proposed. The algorithm performs different levels of color level quantization on different regions of the image according to the human eye color difference threshold. The quantization process which combines the Floyd-Steinberg error dithering algorithm can remove visual redundant data. Finally, the algorithm verification is completed on the FPGA (Field-Programmable Gate Array) hardware platform. The results show that the average bit compression rate of the algorithm can reach 61.65%, which can effectively reduce the amount of transmission data required for VR (Virtual Reality) images.

In the dual-camera phase retrieval method, the phase information is calculated by over-focus and under-focus images obtained through a single exposure after dual-cameras are installed on an inverted microscope. However, due to the processing error of the eyepiece and the installation error of the cameras, translation and rotation exist between the images, resulting in inaccurate phase retrieval results. In this regard, we proposed a dual-camera phase retrieval algorithm based on registration restoration and transport of intensity equation in this paper. Firstly, the defocusing image was registered. Then, image restoration was introduced to fill and restore the black cavity area caused by the registration. Finally, the transport of intensity equation under boundary conditions was used to acquire the high-precision phase retrieval results. The correlation coefficient of the simulation experiments reached 0.9309. In the experiment with a microlens array, the relative error between the restored result and the actual result was 2.8%, which proved the correctness and effectiveness of proposed method.

We propose a method of measuring the three-dimensional (3D) deformation of marine propellers based on 3D digital image correlation technology. The measurement system is composed of a binocular stereo cameras, a flash, and a synchronization device, and a propeller is loaded by a cavitation tunnel. First, the self-calibration method based on epipolar constraint is used to calibrate the external parameters of the system to obtain the 3D displacement distribution of the blade surface. Then, the point cloud registration is performed on the reconstructed hub, we acquire the translation vector and rotation matrix of the point cloud at the deformed blade root to eliminate the rigid body displacement caused by different hub positions. Finally, the refracted light paths through air, glass, and water are constructed, and refraction correction is performed on the reconstructed 3D coordinates of the object point to obtain the real 3D shape of the blades in the cavitation tunnel. Measuring the propeller deformation in the cavitation tunnel with our method can get the full-field 3D displacement distribution of the propeller blades at a fixed phase, which provides a feasible non-contact full-field scheme for measuring the deformation of marine propellers.

Segmented mirror co-phasing is one of the key techniques in the development of large-aperture telescopes, and its accuracy mainly depends on the measurement accuracy of the edge sensors. Aiming at the co-phasing requirement of large-aperture segmented mirror telescopes, we proposed the design scheme of an edge sensor based on equal thickness interference. Then, the basic principle was expounded and the structure diagram of the edge sensor was provided. Furthermore, data fitting and image processing were applied to the scheme simulation. The results show that the measurement accuracy of this scheme can reach a tilt/tip error of 0.02″ and a piston error of 20 nm, meeting the co-phasing detection requirements of large-aperture segmented mirror telescopes.

To solve the problem that the traditional dual-frequency method cannot meet the requirement of high precision measurement, an enhanced dual-frequency phase unwrapping method based on the regional quantification algorithm is proposed. In this method, unstable fringe orders are first obtained by the dual-frequency method, and the fringe orders are divided by the regional gray-code map. Then, the fringe orders corresponding to all the pixels in each region are sorted and the median value is obtained. Finally, the obtained median value is assigned to the corresponding the fringe orders of all pixels in this region. The quantified fringe order is unique and stable, so the method can obtain accurate absolute phases. Simulation and experimental results demonstrate the feasibility of the proposed method. Compared with the traditional dual-frequency method and three-frequency method, the proposed method reaches the measurement speed as that of the dual-frequency method and the measuring precision as that of the three-frequency method.

In this paper, we proposed a high-precision centroid location algorithm based on cubic spline fitting and interpolation combining the advantages of centroid algorithms and surface fitting algorithms. Besides, the principle behind its double error suppression was given. The simulation showed that the location error of the proposed algorithm at different SNRs was significantly smaller than that of traditional centroid algorithms. When the SNR was 20 dB, the root-mean-square error of the proposed algorithm was only 0.003 pixel. Furthermore, the star images from real instruments verified the effectiveness of this algorithm once again. In summary, this algorithm can effectively suppress the location error and has strong noise resistance, which can be widely applied without requiring specific star models.

The output characteristics of a passively Q-switched pulse laser with a large core size crystal waveguide are studied experimentally. Using Yb∶YAG with core size of 320 μm×400 μm and an atomic number fraction of 1%, Er∶YAG with cladding size of 7 mm×30 mm and an atomic number fraction of 0.5%, a single-clad rectangular crystal waveguide with a length of 77 mm, and a Cr 4+∶YAG saturable absorption crystal with initial transmittance of 85%, a passively Q-switched pulse energy of 0.84 mJ@8.7 kHz, a pulse width of 23.8 ns, and a beam quality of M2=1.12×1.06 is obtained. Experimental results show that the high peak power pulse output with near diffraction-limit can be obtained by passively Q-switched pulse laser with large core diameter crystal waveguide.

In this paper, we introduced a light-transmitting fiber with a large numerical aperture and core diameter to solve the problem that the traditional measurement systems for laser spot distribution restricted the incident angle of beams. Then, the fiber array was arranged as the front end of spot sampling in the system, so as to increase the allowable incident angle range and analyze the associated light-transmitting characteristics. Furthermore, we analyzed the influencing factors of optical fiber transmittance and studied the tolerance for the incident angle of optical fiber transmission and the consistency of optical fiber as an array unit by combining numerical analysis method and experimental measurement. This verified the feasibility and superiority of optical fiber applied in the measurement systems for laser spot distribution. The results can provide an effective theoretical basis for the establishment of perfect optical fiber integrated equipment and its application to the relevant laser measurement systems.

The accuracy and stability of semiconductor laser’s output are greatly affected by temperature, temperature change will lead to the change of threshold current, electro-optic conversion efficiency and wavelength, and then affect the output power of semiconductor laser. As such, we designed a temperature control system for the normal operation of the semiconductor lasers at set temperature. This system uses a single chip microcomputer as the core control element, a thermoelectric cooler and a PTC heater as the executive elements, an AD590 temperature sensor and a PT1000 platinum resistor as the temperature detection elements. It controls the temperature by outputting pulse width modulation waves with different duty cycles through the variable-domain fuzzy proportional-integral-derivative (PID) control algorithm. Through simulation analysis, this control algorithm can not only reduce the system overshoot, but also possesses strong robustness. Experimental results indicate that the system can achieve the required temperature control precision of ±0.1 ℃ in the range of -12 ℃ to 120 ℃ and reach the target temperature within 250 s.

The single-pass optical parameter mid-infrared(MIR)ultra-short pulse generation scheme based on the all polarization-maintaining fiber is verified experimentally. Based on the all-fiber master-oscillator-power-amplifier(MOPA)structure, an adjustable repetition rate near-infrared pulse is achieved with average power of 2.4 W, pulse width of 48.85 ps, and center wavelength of 1029.75 nm. When the repetition rate of the system is set as 100 kHz, the peak power of the near-infrared pulse can reach 491 kW. When the average power of the incident pulse is 608.9 mW, a mid-infrared picosecond pulse with an average power of 66.13 mW and corresponding peak power of 13.5 kW is obtained by pumping the MgO-PPLN crystal using the near-infrared pulse. By adjusting the crystal reversal period and temperature, the tunable wavelength output of 3180-3976 nm can be achieved. The proposed scheme has the characteristics of simple structure and high stability.

The particle streak velocimetry (PSV) method based on binocular vision and single-frame multiple exposure was proposed in this paper. To be specific, the velocity direction was judged by the combination of long and short exposure and the gray-level fitting was used to identify the trajectory features. In addition, the trajectory midpoint was employed to calculate the particle velocity in order to improve the measurement accuracy. This method adopted nearest neighbor matching and angle of inclination constraints to match and sort multiple trajectories of the same particle, epipolar constraints to accomplish binocular matching based on trajectory feature points, and B-spline fitting of the three-dimensional reconstructed feature points to calculate the three-dimensional velocity of particles. The multi-exposure PSV method can simplify binocular matching. As a result, an experimental system and the corresponding image processing flow were formed for binocular multi-exposure PSV. We applied the small luminous holes to verification experiments at different three-dimensional velocities and analyzed the influence of different trajectory feature points on the velocity measurement. The results show that the average relative error obtained by the trajectory midpoint is less than 4.2%, and the standard deviation is small, demonstrating the advantage of velocity calculation with the midpoint rather than with the end. The actual measurement of the flow field in a water jet test bench indicates that this method can be reliably used for three-dimensional flow field measurement.

Aiming at the problem of poor robustness and accuracy in the initialization of monocular visual simultaneous localization and mapping (SLAM), this paper proposes a robust initialization method based on point and line features. First, the line features are extracted and matched between two frames. Then, the initial rotation matrix and translation matrix between the two frames are optimized by maximizing the overlap length of the projected line features. Finally, a sliding window is used to increase the number of initial image frames, and the initial map and the estimated keyframe pose are optimized based on information and constraint of multi-frame images and the global bundle adjustment method. The test results on the TUM and OpenLORIS datasets show that compared with traditional initialization methods, the method is more robust and accurate, and can quickly complete high-precision initialization in challenging scenarios.

To address the problems associated with excessive time consumption and large errors in irradiance equation solutions using existing shape-from-shading (SFS) algorithms for three-dimensional (3D) reconstruction of hybrid surfaces under perspective projection, a fast SFS algorithm based on the Newton-Raphson method is proposed. First, the Blinn-Phong model is adopted to characterize the hybrid reflection property of object surfaces. Then, an image partial differential irradiance equation that corresponds to the 3D shape information of the surfaces is established by considering the pinhole camera perspective projection model. Second, the irradiance equation is transformed into a functional equation in the height gradient of object surfaces, which is iteratively solved using the Newton-Raphson method. Then, the solution is converted into a Hamilton-Jacobi partial differential irradiance equation whose Hamiltonian function can be obtained through Legendre transformation. Finally, a scheme to approximate the Hamiltonian function based on optimal control theory and iterative fast marching strategy is applied to obtain the viscosity solution of the Hamilton-Jacobi equation, which represents the heights of hybrid reflection surfaces. Experimental results demonstrate that the mean absolute error and root mean square error of the heights of the object surface decrease and the run time of the proposed algorithm is greatly reduced compared with the existing SFS algorithm for 3D reconstruction of hybrid surfaces based on the upwind scheme.

This paper investigated the influences of K-Cs antisite, K-Sb antisite, and Cs-Sb antisite on the electronic structure properties and optical properties of K-Cs-Sb photocathodes by the first-principles method based on density functional theory. Besides, we analyzed the electronic structure properties such as energy band structure, density of states, and formation energy, and the optical properties such as refractive index, extinction coefficient, and absorption coefficient associated with different defect models. The calculation results regarding the electronic structure properties show that the K-Cs-Sb antisite defect models with Sb occupied by excess alkali metal have indirect band gap structures and take on the nature of an n-type semiconductor. In contrast, the K-Cs antisite defect models and the K-Cs-Sb antisite defect models with alkali metal occupied by excess Sb exhibit the nature of a p-type semiconductor. The antisite defect model of K2Cs0.75Sb1.25 is easier to form and more stable than its counterparts. In addition, the calculation results regarding optical properties demonstrate that the absorption coefficient peak shifts to the lower energy position due to excess alkali metal, while the situation is just opposite for excess Sb metal. In the energy range (i.e., 2.4-3.2 eV) of the neutrino-scintillator interaction, K2Cs0.75Sb1.25, which has the largest absorption coefficient and the smallest refractive index, is a better choice as photoemission materials than traditional K2CsSb.

The writing process of photorefractive dynamic gratings in InP∶Fe was described with nonlinear carrier transport equations based on a one center-two band model, which were then linearized by perturbation. As a result, the steady-state space charge field in a small-modulation interference pattern was solved, and the relationship between the space charge field and the gain coefficient was established by coupled wave equations. Furthermore, the effects of temperature, pump intensity, external direct current (DC) electric field, and incident angle on the gain coefficient were examined. It turns out that the gain coefficient exhibits temperature-intensity resonance and the optimal pump intensity is strongly dependent on the operating temperature of crystals. The gain coefficient can be significantly improved by an external DC electric field and the gain increases linearly with the enhancement of the electric field below 10 kV·cm -1. There is an optimal incident angle in the case of temperature-intensity resonance. The optimal pump intensity is 218 mW·cm -2 and the optimal incident angle is 5° at the temperature of 298 K and the external electric field of 5 kV·cm -1. Also, we experimentally investigated the relationships of the pump intensity, external DC electric field, incident angle with the gain coefficient through two-wave mixing in InP∶Fe. The results show that the change rule of the gain coefficient agrees with the theoretical predictions, verifying the rationality of the one center-two band model. This work has an important reference value for the research on the two-wave mixing of III-V semiconductor photorefractive crystals.

In order to achieve highly efficient nonlinear conversion through the design of optical elements, a structural unit composed of an Au nanoring, an Au split-ring resonator (SRR), and four GaAs nanorods is proposed to form a nanoring disk resonant cavity and a hybrid structure metasurface of the open resonant ring. The SRR and nanoring jointly excited Fano resonance to enhance the local electric field. The four GaAs nanorods with high second nonlinear polarizability in subatoms are used as second harmonic generation converters to reduce the absorption loss and improve the nonlinear conversion efficiency. Furthermore, the mode matching of dipole resonance at both the fundamental frequency and the second harmonic improves the nonlinear conversion efficiency. The efficiency for second harmonic generation is up to 0.15% through simulations. Therefore, this research provides new ideas for the exploration and design for novel optical components with high nonlinear conversion efficiency.

We proposed an integration method based on two-dimensional Taylor expansion, in which the terms in the first two orders were used to approximate the height difference between two points. Combining the approximation relation between the first-order term and the second-order one, we derived a new difference operator, which was applied to the zone method. In addition, we proposed a non-iterative method to calculate non-matrix height. Numerical results show that when the sampling points are distributed in the barrel and pillow shapes, the reconstruction accuracy of the proposed method is 0.1-0.2 μm, which is better than that of other methods (0.5-0.7 μm). For the reconstruction of non-matrix data with 29236 sampling points, the calculation time of our method is about 0.1 s, significantly shorter than that of the iterative methods, and it is much shorter as the number of sampling points increases.

In this paper, we proposed a method of evaluating the stress birefringence of fused silica in the deep ultraviolet waveband, in which the stress at several cross sections in the optical element was obtained by finite element simulation. Furthermore, the total phase retardation and azimuth introduced by the mechanical stress were calculated by three-dimensional interpolation fitting, Jones matrix, and path integration. Without considering the parallelism error of the element, the numerical results of phase retardance and azimuth at 632.8 nm were in good agreement with the experimental results, which verified the accuracy and effectiveness of the proposed method. On this basis, we derived the variation in the stress birefringence at 248 nm and 193 nm under the same loads, which can be used to analyze the effect of stress birefringence in optical elements on the polarization of optical systems.

Boson sampling can effectively simulate the sampling problem based on quantum effects, which provides a new path to verify the exponential acceleration of quantum computation. In reality, it is difficult to prepare large-scale photons with indistinguishable properties, which greatly suppresses the computational complexity advantage of boson sampling. In order to study the influence of photon partial distinguishability and photon losses on the probabilities of boson sampling, the boson sampling process based on the Reck model with 6 photons and 10 modes is simulated. The experimental data indicate that with the decrease of the indistinguishability and the increase of photon loss probabilities, the error between the actual frequency of output combinations and the ideal one increases gradually, however the error variation speed decreases. When the partially distinguishable photon number is changed from 0 to 1, the error variation range for boson sampling output combinations is the largest. The accuracy for boson sampling output combinations gradually decreases with the further increase of partially distinguishable photon number, but the reduction speed decreases. Our results demonstrate that boson sampling based on the Reck model is sensitive to photon indistinguishability, partially distinguishable photon numbers and photon losses in optical networks.

In this paper, we presented the basic principle and fabrication method of an integrated optical waveguide current sensor based on a micro-ring resonator coated with Fe3O4 magnetic nanoparticles. In the alternating magnetic field generated by the measured current, Fe3O4 nanoparticles produce energy loss, and then the temperature changes. As a result, the refractive index of the waveguide varies. Current sensing can be realized by monitoring the drift in the resonance wavelength output from the micro-ring resonator. We reasonably designed the key parameters by the finite difference time domain method to obtain a wide-range and high-quality micro-ring resonator and thus prepared current sensors with different micro-ring radii. The theoretical and experimental results show that the drift in the resonance wavelength is proportional to the square of the current amplitude and frequency respectively when the measured current amplitude is 0 to 0.5 A and the frequency is 0 to 60 kHz. Besides, with the decrease in the micro-ring radius, the detection range of the sensor increases and the sensitivity drops. This paper can provide a theoretical basis for the integrated miniature current sensors and promote the development of silicon-based photoelectric sensors.

The existing deep learning based SAR-assisted cloud removal methods do not take full into account the texture and spectral information of the optical images, which results in blurring and spectral loss. In this paper, we constructed a data set for SAR-assisted cloud removal based on the Sentinel-1 and Sentinel-2 satellite images in Yuhang District of Hangzhou. In addition, we established a conditional generative adversarial network (cGAN) based model by fully considering the details, texture, and color information of optical remote sensing images, achieving information recovery and reconstruction in the case of optical images covered by thin clouds, fog, and thick clouds. The results show that the proposed method outperforms other methods in SAR-assisted cloud removal.

In order to distinguish the two kinds of surface defects, particulate dust above the surface and bubble particles below the surface, we establish two polarization transmission models of surface defects according to the Fresnel transmission law and Mie scattering theory, combined with the Mueller matrix. Through simulation analysis, the influence of component refractive index, defect type, defect size, incident wavelength, and incident angle on the polarization transmission characteristics of the two surface defect particles is obtained. Finally, the experimental verification proves that the model has high accuracy and is important both in theoretical research and engineering.