A fully etched Bragg grating filter based on Silicon-On-Insulator(SOI) waveguide is proposed. The full-etched feature makesthe tuning on Bragg wavelength more sensitive and efficient, which can be fabricated by one-step top silicon etching. The simulation results show that the wavelength-period tuning coefficient of 33 nm/nm and 11 nm/nm for the first- and third-order gratings are obtained respectively,groove refractive index tuning has a coefficient of 1 nm/0.006. Combining low refractive index contrast of grating bar and groove with higher grating order, the full-etched grating filter with a narrower bandwidth at 1 550 nm band can be realized.

In order to understand the process of phase graing imaging intuitively and deeply, a new analysis method was proposed, which is called as the Principal Diffraction Orders Analysis (PDOA). The key point of PDOA for analysing the imaging of the phase grating is focusing on the principal diffraction orders of phase grating, while ignoring the non-essential diffraction orders, which will greatly simplify the analysis of the phase grating imaging. The analysis result of PDOA indicates that for a π-phase shift grating with 50% duty cycle, the principal diffraction orders are ±1 diffration orders, but ±3 diffraction orders are also necessary. And for a π/2-phase shift grating with 50% duty cycle, the zeroth diffraction order is not merely creating annoying background radiation. It is as important as ±1 diffration orders of phase grating.

At present, the deflection angle of orthogonal cascaded liquid crystal polarization grating is considered to be an integral multiple of its angular resolution. Actually , there is deviation between the actual deflection angle and the design angle of the orthogonal cascade liquid crystal polarization gratings. To solve this problem, the deflection angle formula of cascaded liquid crystal polarization gratings is derived according to the angle deflection theory of single-chip liquid crystal polarization gratings firstly, and then the deflection angle model of two-dimensional orthogonal cascaded liquid crystal polarization gratings is derived, the relationship between the deflection range and the angle resolution of two-dimensional orthogonal cascaded liquid crystal polarization gratings is analyzed, and the actual angle resolution satisfying a certain angle range, the angle range that satisfying the actual angle interval and the design angle interval that satisfying the angle range and angle interval at the same time is calculated respectively. Finally, A software model which measurement accuracy is 0.1° is established use optical design software and a construction which measurement accuracy is 0.1° are established,they prove that the angular deflection model is accurate.

Because the infrared image lacks certain texture information, most target detection networks cannot achieve great detection results for infrared images. This paper proposes a cross-domain fusion network structure that combines multiple modal for infrared target detection. Using image conversion network without pairing, modal conversion of existing infrared dataset to generate a pseudo-visible light dataset. Then, this paper proposes a dual-channel multi-scale feature fusion structure in the infrared domain and the pseudo-visible light domain, uses feature pyramid network to obtain the feature map of each mode, and performs dual-modal feature fusion for multi-scale features. Finally, in order to make up for the lack of texture in the fusion process, this paper proposes a soft weight distribution module. By splicing the parameterized source domain, target domain and fusion domain features, the network weight is assigned and optimized through learning, thereby improving the accuracy of feature extraction and target detection. The experimental results show that the method in this paper has better infrared target detection performance compared with the conventional method.

In order to solve the problem that infrared small target detection algorithm is easy to detect falsely at the edge and inflection point of complex background, an infrared small target detection algorithm based on the fusion of local contrast and non-local low-rank tensor model is proposed in this paper. First, Double window local contrast measure algorithm is used to extract the local prior information of target and background. Then, under the constraints of local prior information obtained, the standard IPT model was reconstructed, and weighted tensor nuclear norm minimization was introduced to suppress the background and improve the iteration efficiency. Finally, the separation problem of target and background is transformed into a tensor robust principle component analysis problem, and alternating direction method of multipliers is used to solve this problem. Experimental results show that the performance of the proposed method is better than the existing typical infrared small target detection methods under different complex backgrounds.

Considering that the current space target detection technology has some problems in target recognition, which are high false alarm rate and low algorithm efficiency, a space target recognition method based on Adaptive Spatial Filtering Multistage Hypothesis Testing (ASMHT) algorithm was proposed, which is used to extract space targets from star image in the sidereal tracking mode in photoelectric observation system. The method includes two processes of target coarse screening and target fine screening. Target coarse screening uses Gaussian difference function based on the scale space to get the scale value of each candidate target in the preprocessed image. The scale value is also set to the size of the spatial filtering window, and the gray correlation criterion is replaced by the gray distribution characteristics as the accordance of different kinds of targets in the spatial filtering window. The background stars without image motion and random noise are removed, and the suspected moving targets are screened out. The improved multistage hypothesis testing method is used in target fine screening, in order to greatly improve the efficiency of the algorithm, the speed window of candidate targets are established and the space targets are selected according to the trajectory characteristics. The experimental results of space target in simulation image show that, compared with the existing space target recognition methods, the ASMHT algorithm has the ability of target detection under the condition of space targets in low SNR, and the comprehensive detection performance is the best, which can also obtain higher detection rate under the same false alarm rate. Real star image test results show that the ASMHT algorithm has lower computational complexity and achieves more accurate space target recognition.

Collecting infrared images from fields is difficult, high-costing and time-consuming. In order to address this problem, an infrared image generation method based on conditional generative adversarial networks is proposed. In the proposed method, the D-LinkNet network is utilized to build the generative model, enabling improved learning of rich image textures and identification of dependencies between images. Moreover, the PatchGAN architecture is employed to build a discriminant model to process the high-frequency components of the images effectively and reduce the amount of calculation required. In addition, batch normalization is used to optimize the training process, and thereby the instability and mode collapse of the generated adversarial network training can be alleviated. Finally, experimental verification is conducted on the produced infrared/visible light dataset. The experimental results reveal that high-quality and reliable infrared data are generated by the proposed algorithm.

Based on scanning probe microscope, a set of scattering scanning near-field optical imaging device is designed. The structure of the device and the basic near-field signal detection principle are introduced, andthe influence of the demodulation order, focus spot size and other factors on the near-field optical signal extraction are discussed through models and experiments. In order to verify the performance of the device, a sample of gold nano-particles and a sample of h-BN microcrystals be characterized. The results show that the home-made device achieves a spatial resolution of 10 nm, and the standing wave phenomenon formed by the h-BN phonon polarization excimer can be clearly observed, demonstrating the huge application potential of this technology.

According to the requirement of long focal length and compact optical system for airborne platform, a catadioptric system with long focal length and high resolution is designed by using an improved R-C mirrors and a spherical correction lens to correct spherical aberration, coma and chromatic aberration in full field. This system has a focal length of 1 500 mm and field of 2°. The envelopment diameter of the optical system is no more than φ400 mm, the Modulation Transfer Function is better than 0.56 @62.5 lp/mm, and the imaging quality is approaching to diffraction limit. In order to improve efficiency and reduce the difficulty of alignment, the imaging quality of the central and adjacent field of the R-C primary and secondary mirror is controlled to diffraction limit. The sensitivity matrix of the mapping relationship between the misalignment and primary aberration is established by means of interferometer detection and computer-aided alignment. The aberration characteristics of the misalignment optical system are analyzed. The optical precise alignment scheme of wavefront accurate measurement and inversion of the misalignment is proposed. After alignment, the RMS value of the whole system is better than 1/13λ, achieving the imaging quality requirements.

The design of the cooled infrared system can not avoid the problem of cold reflection, so it is necessary to complicate the optical system to weaken the influence of cold reflection. By analyzing the cold reflection characteristics of the cooled infrared system, the differential threshold cold reflection correction method is proposed, which can relax the restrictions on the cold reflection in the optical design stage, without considering the cold reflection. After the system is optimized, ray tracing is carried out to simulate the cold reflection phenomenon in the real scene, and then the cold reflection is eliminated by this method. A cooled infrared optical system is designed. After using this method, the image is clear subjectively, and many image quality evaluation functions are improved objectively. The results show that this method can effectively reduce the cold reflection of the cooled infrared system, simplify the design of the optical system, and is of great significance to the miniaturization and lightweight of the system.

To achieve a highly stable strontium atomic optical clock, the ultra-stable laser system based on 30 cm cavity is desiged. Systematic evaluation and suppression of the main noise in the system is performed, so that the current vibration insensitivity of the reference cavity is reduced to 6×10-10/g with the corresponding frequency instability less than 3.6×10-16. By using the method of temperature control in the vacuum chamber, the temperature changes is less than 0.4 mK in a day, and the temperature fluctuation of the cavity is 5 orders of magnitude lower than the laboratory environment temperature at 1 Hz. The power jitter is suppressed to 1 pW, and the corresponding frequency instability is 2.4×10-19@1 s. The residual amplitude noise and fiber phase noise are less than 3×10-16 after being suppressed, which fully meets the requirements for ultra-stable lasers of the order of 10-16. Comparing the beat frequency with a 10 cm cavity ultra-stable laser system, comprehensive beat frequency results and noise analysis show that the stability of the laser frequency instability is less than 6.2×10-16@1s after the system locked.

Based on the modulation transfer spectroscopy technique, the frequency locking of the distributed feed back laser on the 87RbD2 line F=2→F?=3 is realized, and the multi-parameter pairs such as modulation frequency, demodulation phase and pump light polarization are theoretically and experimentally studied. Modulating the effects of the shifted spectral signal provides a basis for selecting and optimizing the modulation transfer spectral stabilization technique. The results show that the best frequency locking signal can be obtained when the pump modulation frequency is between 9~15 MHz and the phase change of the modulation signal is near π/5. In the experiment, when the modulation frequency is 12.5 MHz, the polarization angle of pump and probe light is 90o, and the applied magnetic field is 5 Gs, the amplitude and zero slope of modulation transfer spectroscopy signal are optimized by optimizing the demodulation signal phase and proportion, integral,differential control parameters, and the high-precision frequency locking of DFB laser is realized.The frequency line after the frequency-locked laser is about 1.6 MHz, and the frequency stability is less than 1.75×10-9, it can be used as a light source in the cold atom interference experiment.

Core-shell structure ZnO/g-C3N4 nano-photocatalysts with ultrathin amorphous g-C3N4 layer were synthesized via facile polymer network gel method applying zinc oxide and dicyandiamide as the raw materials. When the molar ratio of zinc oxide to dicyandiamide was 1∶1, the heterojunction interface of the composite with ~3 nm thickness of shell layers was distinct, and it had the best photocatalytic activity for the degradation of organic dye pollutants under simulated sunlight and visible light irradiation. Ultraviolet-Visible diffuse reflection spectra (UV-vis) results show that the composite materials have increased absorption in the visible light region, as well as the absorption bands are red shifted. Photoluminescence (PL), Stable Surface Photovoltage (SPV) and Stable Surface Photocurrent (SPC) reveal that the loading of g-C3N4 significantly improve the separation of photo-generated carriers. The photocatalytic degradation of Methylene Blue (MB), Methyl Orange (MO) and Rhodamine B (RhB) was carried out under simulated sunlight and visible light. The results exhibit that the photocatalytic activity of ZnO/g-C3N4 composite is effectively enhanced, and the catalyst has excellent stability and reusability. In addition, sacrificial agent experiments proclaim that superoxide radicals are the main active species for composite to degrade pollutant dyes, while holes play an important role in the degradation process. During the photocatalytic process, the core-shell structure can effectively promote the charge transfer between ZnO and g-C3N4. This study provides a simple strategy for the preparation of high-efficiency nano-photocatalysts based on graphitic carbon nitride/metal oxide heterostructure.

When the transformer is overheated or has a discharge failure, characteristic gases such as C1 and C2 gases are dissolved in the insulating oil. There is also a small amount of C3 component gases that may interfere with the detection of other characteristic gases. By analyzing the causes of gas cross-interference and the infrared absorption spectra of C1, C2, and C3 component gases, the gas absorption coefficients within the filter bandwidth were studied and the interference coefficients of C3H8 and C3H6 gases to C1 and C2 gases were theoretically calculated. According to the analysis results, the parameters of the optical filters were determined. A photoacoustic spectroscopy based multi-component gas analysis system using infrared thermal radiation source and non-resonant photoacoustic cell was built. The experimental results show that the interference coefficient of C3H8 gas to CH4, C2H6, C2H4, C2H2 is 3.78%, 84%, 1.5% and 1.6%, respectively. The interference coefficient of C3H6 gas to CH4, C2H6, C2H4, C2H2 is 2%, 32%, 69.6% and 2.6%, respectively. This research is of great significance for evaluating and guiding the improvement of the technical performance of photoacoustic equipment for dissolved gas analysis in transformer oil.

Based on multiconfiguration Dirac-Fock method, the high-resolution 2p photoelectron spectra and satellites originating from the corresponding shakeup transitions during the photoionization of neutral sodium atoms are theoretically studied. The main features of photoelectron spectra from the normal photoionization and strong shake-up transitions are presented and interpreted. It is shown that the electron correlations of the 2p hole affect the energy positions of photolines and give rise to considerable structures in the photoelectron spectra. The reasonable agreement between the measured results and simulated spectra confirms the reliability of the theoretical approaches and enables us to assign the observed photolines.

In order to study the effect of base pressure on the microstructure and optical properties of Yb/Al multilayers, a series of SiC/(Yb/Al)3 period multilayers with the same structure were prepared by DC magnetron sputtering under base pressure conditions of 4×10-5 Pa, 8×10-5 Pa, 1×10-4 Pa, 2×10-4 Pa and 4×10-4 Pa, respectively. The surface and internal structures of Yb/Al multilayers were characterized by X-ray grazing incident reflection, atomic force microscopy and wide-angle X-ray diffraction. The results show that the average interface width of Yb/Al multilayers decreases from 2.15 nm to 1.82 nm with the raise of base pressure from 4×10-4 Pa to 4×10-5 Pa; the surface roughness decreases from 1.87 nm to 1.43 nm. Yb, Yb2O3and Al polycrystalline grains are formed in the film, and the grain size increases slightly. The stress of SiC/(Yb/Al)3 period multilayer is tensile, and the stress increases from 85 MPa to 142 MPa with the base pressure raising from 4×10-4 Pa to 4×10-5 Pa. The reflectivity of the sample prepared under 4×10-5 Pa base pressure was measured. When the wavelength is 73.6 nm and the incident angle is 5°, the reflectivity of the sample is 31.3%.

Notch filters are widely used, but the difficulty lies in the large amount of calculation and complex film structure and material types when using the traditional transmission matrix method for spectrum design. In this paper, the special dispersion relation of the multiple Bragg scattering of the periodic potential field Bloch wave in the crystal in the solid state physics theory is combined with the Maxwell equations in the optical film theory to calculate the periodic function of the one-dimensional photonic crystal (ie film) and obtain the band structure; the change of the forbidden band width and position in the energy band structure corresponding to the change of the medium refractive index (medium refractive index ratio), center wavelength and incident angle is analyzed; the specific functional relationship is deduced. Bring the spectral requirements of the notch filter into the functional relation for calculation, and bring the result into the Essential Macleod thin film design software for film system design. Compared with the traditional transfer matrix method, the results show that the design method based on the one-dimensional photonic crystal band structure is much less computationally intensive, the periodic structure is simple, and only two materials are needed. The spectral curve can meet the design requirements.

In order to obtain more precise icing thickness distribution within a span, a special icing monitoring technique for tight tube Optical Fiber Composite Overhead Ground Wire (OPGW) is proposed and preliminary verified by experiments. This method utilizes the distributed strain sensing capability of Brillouin optical time domain reflectometer. The strain distribution of OPGW was obtained by measurement, and then the weight distribution was derived based on mechanical analysis method. the specific icing thickness distribution was obtained via the conversion between weight and icing thickness. In the simulation with a suspended optical cable, the errors of the experimental results are 2.27% and 15.77% for two uniform loadings of 5 kg and 2.5 kg, which preliminarily verifies the effectiveness of the proposed method. The error analysis shows that the effect of the proposed method is better for longer span range in practice, because it allows longer spatial resolution which can improve the strain measurement accuracy.

Taking panda-type polarization-maintaining fiber as the object, the influence of drawing tension and heat treatment on its stress birefringence is systematically studied. In the multiphysics finite element modeling, we introduced the drawing tension during the fiber preparation process into the PMF photoelastic model, and we summarized the numerical law that the birefringence of the panda-type PMF decreases linearly with the increase of the drawing tension. We used white light interferometry to experimentally measure the effects of different heat treatment conditions on the birefringence of PMFs. The structural relaxation induced by boron-doped silica glass at high temperature causes the volumetric shrinkage of the Stress Applying Parts (SAP), which increases the birefringence. The deformation caused by the structural relaxation is obtained from the variation of the vacancy defect concentration of the glass network, and then the birefringence after the annealing of the fiber is calculated. The numerical simulation results are consistent with the experimental measurements. This work provides a theoretical basis for the design, preparation and birefringence control of PMF.

A scheme for generating 16-tupling millimeter wave signals is proposed, which uses parallel Mach-Zehnder modulators and optical attenuator without filters. In this scheme, the Mach-Zehnder modulator and optical phase shifter in parallel are used to generate the 8th-order optical sideband, and the 16-tupling millimeter wave signal is obtained through the beat frequency of photodetector. In view of ideal and non-ideal extinction ratio of modulator, when the extinction ratio is 35 dB and 100 dB respectively, the optical carrier and the fourth-order optical sideband are theoretically suppressed, and the eighth-order optical sideband signal is derived. The correctness of this deduction is verified by simulation. Furthermore, according to the simulation results, the influence of non-ideal conditions of various parameters, such as the shift of modulation index and optical attenuator attenuation value, the angle shift of electric phase shifter and optical phase shifter, on the system is analyzed. The 2.5 Gbit/s baseband signal is modulated on the 16-frequency millimeter wave signal generated by the scheme. When the transmission distance of the system is 5 km, 10 km and 15 km, the loss power is 0.35 dBm, 0.55 dBm and 2 dBm respectively, and the transmission loss is small. In addition, the relationship between laser linewidth and received power is analyzed. The received power is -22.6 dBm when the linewidth is 10 MHz, and the power losses are 0.1 dBm, 0.25 dBm and 0.6 dBm when the linewidth is 20 MHz, 30 MHz and 40 MHz, respectively.

A reconfigurable microwave photonic mixing and phase shifting system is proposed. By adjusting the frequency of the local oscillator signal and the angle of the polarizer, it can output up/down conversion microwave signal, and its phase can be adjusted continuously within 360°. In addition, by appropriately changing the phase difference between any two mixing channels, it can be reconstructed to realize I/Q mixing, double-balanced mixing and image rejection mixing. When applied to multiple channels, it can output multi-band mixing and phase-shifted microwave signal, and the phase of each channel can be adjusted independently. Since the high-order sidebands of the local oscillator signal are involved in the mixing, the requirements for the frequency of the local oscillator signal are reduced exponentially. The simulation results show that when the frequency of the local oscillator signal and the RF signal are 10 GHz and 19 GHz respectively, the mixing range of the system is 1~79 GHz, the phase shift amplitude difference is less than 0.1 mV, the image rejection ratio exceeds 65 dB, and the signal power difference after multi-band mixing is less than 0.2 dB. In addition, the 90° electrical phase shifter and polarization controller angle adjustment deviation hardly affect the system performance, and the appropriate radio frequency signal power can help improve the system performance. Theoretical analysis and simulation have verified that the system has high flexibility, reconfiguration and practicability.

In order to improve the recognition accuracy of intrusion vibration events by distributed optical fiber acoustic sensing system based on phase-sensitive optical time domain reflectometer, a recognition method of fiber optic vibration signals using endpoint detection and signal recombination is proposed. The method first uses EMD_PCC-based denoising to denoise the signal, then performs endpoint detection on the denoised signal, reorganizes the detected vibration signal and extracts the frequency domain information of the vibration signal, uses a dual-input multi-scale convolutional neural network to extract the time domain features and frequency domain features of the vibration signal respectively, and finally uses a support vector machine for classification. The experiment proves that the recognition method can quickly complete the training of the recognition model and effectively recognize the intrusion vibration signals collected in the actual environment, and the recognition accuracy of the intrusion signals can reach 94.8%.

A simple aspheric chromatic dispersion lens group of low cost is designed using Zemax, and an integrated fiber-coupled chromatic confocal 3D measurement system is developed. Performances of four peak wavelength extraction methods, i.e. the maximum method, centroid method, Gaussian fitting method and spline interpolation method, have been compared and analyzed quantitatively. In addition, calibration accuracy of Gaussian fitting method and spline interpolation method is tested and compared through the axial resolution and displacement measurement experiments. The experimental results show that the axial measurement range of the built system is 1 mm. The Gaussian fitting method has higher accuracy and better stability among the four peak extraction algorithms. The axial resolution of the system using Gaussian fitting based and spline interpolation based calibration methods can both reach 0.2 μm and the displacement measurement accuracy is better than 1% within the whole measurement range; a quartz glass with a thickness of 0.219 mm is measured, and the relative measurement error of the average value is 0.5%. Finally, the developed system is applied to the 3D surface measurement of a step structure, a flexible electrode and a MEMS unit, and the experimental results indicate that the proposed system can perform high-precision 3D measurements of complex microstructures and transparent material thicknesses.

In order to solve the problem of registration of spatial objects with unobvious same-name feature points in the scanning at different sites or adjacent 3D field scenic spots, a point cloud registration method based on the center of gravity feature transformation is proposed. Firstly, the gravity centers of the point sets are calculated for the target point cloud and the point cloud to be registered, respectively. And then, the distance from the point set to the gravity center is calculated and arranged in ascending sort. According to the closest point and the farthest point, two feature vectors are constructed and the third feature vector is synthesized. Thus, the point set features of the two scenes can be described as three corresponding feature vectors. The rotation matrix is solved based on the rotation invariance of the matrix so as to solve the translation matrix and accomplish the initial registration. Finally, precise registration of the point cloud is done using the improved ICP algorithm. The proposed algorithm is analyzed experimentally with a plurality of registration algorithms, and the results show that the proposed algorithm is superior to the classic ICP algorithm in registration speed and precision, and highly practicable since it can effectively solve the registration problem of space targets with unobvious same-name feature points in the matching of point clouds at adjacent 3D scenes.

Aiming at the low efficiency of traditional orthogonal iterative algorithm, an improved orthogonal iterative algorithm is proposed to measure the pose of space objects based on monocular vision. Firstly, based on the traditional orthogonal iterative algorithm, the translation vector in the iterative process was eliminated. The initial value of the rotation matrix was solved by using the parallel perspective model instead of the weak perspective projection model, so as to accelerate the solution process of the orthogonal iterative algorithm. Secondly, simulation experiments are used to study the effects of the extraction accuracy of the imaging point, the accuracy of three-dimensional coordinate of the space feature point, the calibration accuracy of the camera principal point, the calibration accuracy of the camera focal length and the number of space feature points on the accuracy and efficiency of the algorithm. Based on the results of the simulation experiments, Taguchi method is used to quantitatively analyze the influence of each factor on the accuracy of the algorithm, and find out the factor that has the greatest influence on the accuracy of the improved orthogonal iteration algorithm. Finally, the performance of the proposed improved orthogonal iteration algorithm is tested by the physical experiments. The physical experiments prove that the proposed method is accurate, and takes shorter run time than that of traditional orthogonal iteration algorithm. Based on the results of the orthogonal experiment, the accuracy of the improved orthogonal iteration algorithm could meet different demand of different space task by controlling the different influence factors.

The ceramic filter quality detection mainly relies on manual inspection, which has various problems such as low efficiency and poor accuracy. In order to solve these problems, a method based on multi-scale edge fitting was proposed. The idea of multi-scale was introduced to realize the edge detection on multiple scales, and the edge screening strategy was designed to effectively reduce the influence of irregular edge on line fitting. Firstly, an edge detection method based on multi-scale is proposed to accurately extract the edge. Secondly, the edge screening strategy based on piecewise linear fitting is designed to screen out the irregular edge. Thirdly, after screening, the weighted least squares method is used to fit the edge. Fourth, on the basis of the precise linear fitting of the edge, by analyzing the characteristics of defects, the distance difference features are extracted and the defect discrimination rules are constructed to detect the shape defects. Finally, the dimension is calculated by the geometric calculation and compared with the dimension of standard ceramic filter to judge the product quality. The experimental results demonstrate that the proposed method can quickly and accurately detect the dimension and shape defects of the ceramic filter.

Subsurface damage of optical components directly affects the laser damage threshold of optical systems, and the damage depth is one of the key parameters for measuring subsurface damage, for which there is no mature and rapid quantitative measurement method. A damage depth measurement method based on fluorescence microscopy stereoscopic imaging is proposed. First, during the processing of optical components, quantum dots are used to mark the subsurface damage; when the laser beam is incident on the surface of the optical component at a certain angle, the marked quantum dots are excited to generate fluorescence; the fluorescence signal of the longitudinal distribution of the damage layer is imaged microscopically by a fluorescence camera, and the fluorescence distribution depth is calculated according to the imaging principle and structural parameters to achieve rapid quantitative measurement of the sub-surface damage depth of the optical component. A series of standard parts are prepared by optical glue and glue dumping process, and comparative verification measurement experiments are carried out, and the results show that the proposed method can measure the damage depth of 55~75 μm with a relative error of less than 8%.

In the light scattering method, the small dynamic range of the scattering signal will directly affect the measurement accuracy of optical element surface roughness. To solve the problem, the image fusion is applied to acquire large dynamic range scattering signal. First, the scattering images of different exposure times at the same position are collected. Then, it is transformed with wavelet transform, the decomposed low-frequency components are fused using the principle of strongest scattering signal, meanwhile high-frequency components are fused using the principle of regional characteristic measurement. The multi-exposure scattering image fusion is completed by inverse wavelet transform. Finally, the large dynamic range scattering signal is processed to obtain the surface roughness value of the component. The results show that the dynamic range of the fused scattering signal is increased by 3 orders of magnitude compared with the unfused scattering signal. The surface roughness of optical elements calculated from the fused scattering signal is consistent with the measurement result of the white light interferometry, which proves the proposed fusion method can be used for large dynamic range scatter signal acquisition and surface roughness measurement of optical components.

An easy-to-use and low-cost method was used to clad an alumina coating onto the surface of a flexible copper mesh in one-step laser treatment, fabricating a modified layer of nanostructures with different roughness on the surface of the mesh to regulate the surface wettability. Transient thermal analysis was introduced to investigate the change of temperature distribution field caused by the reduction of the scan path spacing. It is found that the cladded aluminum coating on the surface of the copper mesh fabricated by the laser scanning path spacing at 10 μm exhibits an α-Al2O3 crystalline form with good durability and separation efficiency exceeding 95% after cyclic testing, delivering water contact angle close to 0° in the air and oil contact angle larger than 160° underwater. To address the oil/water separation needs in microfluidic channel applications, oil-water separation tests and simulations of fluid mechanics were carried out for the pipeline formed by curling the flexible substrate of the separation membrane. Computational fluid dynamics was used to analyze how to regulate the distribution of surface nanoparticles, leading to the redistribution of pressure and velocity fields inside the pipeline, thereby promoting the smooth flow of fluid inside the pipeline and enhancing the oil-water separation performance.

As an electromagnetic wave, optical field can be described by using parameters of amplitude, phase and polarization. Spatial optical field modulation technology enables to generate novel spatially structured optical field by modulating these parameters. Compared with other types of modulation devices, the liquid crystal spatial light modulator has the advantages of high diffraction efficiency, millions of modulated pixels, and real-time dynamic modulation. It has become the mainstream device for spatial optical field modulation. In this paper, we first give an introduction to the principles and algorithms of optical field modulation technology, including single-parameter modulation, complex amplitude modulation, and multi-parameter modulation by using the liquid crystal spatial light modulators. Some applications of these optical modulation technologies in holographic optical tweezers, optical microscopy, optical information storage, optical micromachining, imaging behind scattering media, and optical communication are exampled. Then we discuss the problems to be resolved, the development trends and the development prospects of the technology. The purpose of this paper is to help researchers systematically understand the principle, the latest research progress and the potential application of the optical field modulation technology based on the liquid crystal spatial light modulators, and provide some references for research in this field.

The spectral response range of the high Al-content AlGaN material is in the solar-blind ultraviolet band, but the higher trap density on its surface limits its application on the fields of solar-blind ultraviolet detection. Therefore, the effect of surface modification on the performance of AlGaN-based solar-blind ultraviolet photodetectors was investigated. The chemical self-assembly method was adopted to chemically adsorb octadecanethiol organic molecules on the surface of the Al0.6Ga0.4N wafer to prepare a surface-modified AlGaN-based photodetectors. Compared with unmodified photodetector, this modification process could effectively reduce the adverse effects caused by the surface states of the AlGaN material, reduce the leakage dark current, and significantly improve the responsivity of the device, indicating the realization of AlGaN-based metal-semiconductor-metal solar-blind photodetectors with high performance.

In order to solve the problem of multi-scale and poor real-time performance in optical remote sensing image detection, a remote sensing target detection algorithm based on the adjustable parameter number and receptive field is proposed, which can not only reach high detection accuracy, but also achieve real-time performance. Based on the faster region-convolution neural network, a receptive field adjustable module and a channel number adjustable module are designed to improve the accuracy and speed respectively. At the same time, in order to reduce parameter redundancy, the dimension of the full connection layer changes dynamically according to the number of target categories. Experimental results on remote sensing datasets of DIOR, show that the proposed method is higher than all the comparisons with the highest accuracy, and the detection speed is higher than Faster R-CNN. When our algorithm achieved highest speed, it can achieve real-time requirement with proper precision.

Most existing optical remote sensing scene classification methods based on convolutional neural network mainly perform global feature learning and fail to consider the local features in the scene, which cannot effectively address the large intraclass difference and high interclass similarity. Therefore, a novel remote sensing scene classification method based on two branches of vision transformer and graph convolution network is proposed. Firstly the scene image is divided into patches and the then positional encoding and vision transformer are used to encode the patches. Consequently, the long-range dependencies can be mined. On the other hand, the scene image is converted into superpixels. The convolutional neural networks features of each superpixel are pooled and used to represent the node of the graph structure. Then the graph convolutional network is applied to model the spatial topology relationships. Finally the final feature representation of the scene image are described by the features of the two branches. Experimental results on the optical remote sensing image datasets demonstrate the effectiveness of our method.

Because of the imperfect theoretical model and insufficient experimental verification technologies, the problem of information transmission in the plasma sheath has not yet been resolved. In this paper, the interaction mechanism between X-ray photons and plasma is studied firstly, and a modified theoretical model is provided through numerical calculation and theoretical modeling. Different from the conclusion that X-rays can penetrate plasma without attenuation in the traditional wave model, the modified theoretical model established in this paper points out that the transmittance of X-rays in plasma is closely related to plasma electron density and incident X-ray flux. Secondly, an experimental system was built using a grid-controlled X-ray modulation emission source, a single-photon X-ray detector, and a dynamic plasma generator. Using this system, the non-uniform plasma which electron density ranges from 109/cm3 to 1014/cm3 is generated, and the X-ray communication with 1 Mbps communication rante and 10-5 bit error rate is also verified. The experimental results indicate that the modified theoretical model can explain and predict the experimental phenomena, and the experimental system can provide the solution for solving the communication problems in the plasma sheath.

Based on the theoretical model of the interaction between X-rays and matter, the transmission characteristics of X-rays in an electromagnetic shielding environment are studied, and the feasibility of X-rays communication for information transmission in an electromagnetic shielding environment is theoretically demonstrated. After that, a numerical simulation model of X-ray communication in a shielded environment is established, and the communication parameters of X-rays in an electromagnetic shielded environment are analyzed to achieve the index constraint of the core components. Finally, based on the key technologies of X-ray modulated emission and single-photon X-ray detection, an equivalent verification experiment of X-ray passing through the shielding material is conducted to realize the experimental verification of X-ray communication with a communication rate better than 23 kbps. The results are expected to provide some theoretical basis and experimental foundation for solving the radiation data transmission in a shielded environment.