An ultra-large-caliber hyperspectral ocean water meter composed of an ultra-large-caliber front telescope system and an ultra-large-field-of-view spectrometer is designed. The front telephoto system uses a coaxial three-reflection optical system structure with a diameter of 4 m, a field of view of 0.64°, a focal length of 21.6 m, and a wavelength range of 400 to 1 000 nm. The large field of view spectrometer uses an improved Offner structure with a field of view of 240 mm and a spectral resolution of 10 nm. The detector pixel size is 15 μm × 15 μm, and four detectors are staggered to achieve a width of 400 km. The ultra-large field-of-view spectrometer is in a wide band of 400 to 1 000 nm, and the root mean square value of the dot chart radius is less than 3.9 μm. The MTF of the entire system of the static orbit hyperspectral ocean water meter is greater than 0.52 at 33.3 lp/mm, and each index meets the application requirements.

In order to solve the problems of low spectral efficiency and low laser utilization of existing optical spatial pulse position modulation, a layered spatial pulse position amplitude modulation method suitable for atmospheric laser communication is proposed by combining layering technology with spatial pulse position amplitude modulation. In this method, a small number of additional lasers are added to form a multilayer structure, and the pulse position in the pulse position amplitude modulation is used to carry bit information, and the pulse amplitude is used to distinguish different layers. The principle of system layer mapping, spatial pulse position amplitude mapping and its inverse mapping is descripted in detail. Moreover, the bit error rate expression of the proposed scheme is derived. The Monte Carlo simulation method is utilized to further verify its reliability and compare it with the traditional spatial modulation methods. Simulation results show that the proposed scheme can greatly improve the spectral efficiency and reduce the used laser number. For example, at the same transmission bits, the spectral efficiency of (9,4,8,2)- spatial pulse position amplitude modulation scheme is 16 times that of (32,4,128)- spatial pulse position modulation scheme. When bit error rate is 10－3, our proposal improves the signal-to- noise ratio by about 1 dB with employ less than 1/3 number of lasers that used in the (32,4,128)- spatial pulse position modulation scheme. Among them, the parameters in parentheses respectively indicate the number of lasers, the number of detectors, the order of the modulation method, and the number of layers, which are ignored when the number of layers is 1.

The influence of free evolution time on the Ramsey signal characteristics of a pulsed optically pumped Rb clock based on a compact magnetron microwave cavity was reported, and in addition, the effect of coherence relaxation time on the contrast of clock signal was discussed. When the optimal free evolution time of the atomic clock is about 3 ms, the Ramsey central fringe contrast is as high as 52% and the shot-noise-limit is better than 1.7×10－14(τ=1 s). According to the contrast of the Ramsey signal and the optical density in the vapor cell, both population and coherence relaxation times of Rb vapor cell in the atomic clock are 1.95 ms and 2.45 ms, respectively. The experiment provides a useful basis for improving the performance of the pulsed optically pumped Rb clock.

Aiming at the phase reversal phenomenon in the demodulation process of ultra weak fiber grating hydrophone array, a phase compensation method based on the one- hot finite state machine is proposed to modify the flip signal in realtime in field programmable gate array. The phase of the demodulated signal and its compensation conditions are set in a one-hot coded finite state machine, and the phase compensation of the demodulated signal of the optical fiber interference system is realized through the instantaneous state transition of the state machine at a high clock rate. The power consumption, occupied resources and timing results in the functional simulation and experimental test of various phase compensation methods are compared and analyzed. The results show that the phase compensation method based on the one-hot finite state machine can not only solve the phase reversal problem correctly and ensure the integrity of the signal, but also increase the dynamic range of signal demodulation, and reduce the logic delay of the system by 6%. It has advantages in the high throughput and high clock frequency applications of underwater acoustic fiber sensing demodulation system.

In order to clarify the superiority of hybrid transmission performance in optical wireless transmission system, output characteristics of single energy transmission, single communication, and hybrid transmission were investigated in 0.1 m transmission link with received optical power of 3.5 mW and date rate of laser source of 1 kbps. When the single energy transmission system has a load of 4 kΩ in series with inductance, the maximum output power of the panel is 1.82 mW, when the hybrid transmission system has a load of 5 kΩ in series with inductance, the maximum output power of the panel is 1.82 mW, which is 15% higher than the former. The output signal waveform of the hybrid transmission system is distorted at a low load in series with capacitance. Optimized load can improve the performance of waveform. The amplitude in hybrid transmission system is higher than that of the single transmission system at 1.52 V in same conditions.

In order to take advantage of the ease of demodulation of the intensity-modulated fiber-optic sensor, an intensity-modulated liquid level sensor is proposed. The sensor consists of three no-core optical fibers. Among them, the no-core fiber 1 and no-core fiber 2 are cascaded to form a measuring arm, and no-core fiber 3 constitutes a reference arm. The simulation analysis show that if the length of no-core fiber is shortened by 1 mm, the transmission peak wavelength is increased by 25.46 nm. In the 0~50 mm liquid level range, the measured sensitivities of the sensor in the liquid environments, namely water, 5% NaCl, 10% NaCl and 15% NaCl aqueous solutions, are 0.069 5 dB/mm, 0.074 73 dB/mm, 0.077 49 dB/mm and 0.082 71 dB/mm, respectively. The linearities of the sensor are 0.998 25, 0.998 49, 0.988 11 and 0.995 13, respectively. The proposed sensor can eliminate the influence of optical power fluctuation and ambient temperature variation with good repetition, and maybe has a potential application in the petrochemical industry.

A bidirectional output signal frequency optional radio over fiber system based on coherent detection and digital signal processing technology is presented.The proposed system uses parallel phase modulator and wavelength selector switch structure.In the single source condition, the system realizes the baseband signal or multiple millimeter wave signal outputs for both the down and upstream transmissions.The simulation results prove that for the 20 Gbit/s 16-QAM modulated signal, through 30 km optical fiber transmission,the system output signal frequency of downlink can be selected from 0~60 GHz, and its transmission minimum error vector magnitude is 6.53%(0 GHz)~7.61%(60 GHz); the system output signal frequency of uplink can be selected from 0~120 GHz, and its transmission minimum error vector magnitude is 6.89%(0 GHz)~8.30% (120 GHz). The theoretical analysis and simulation results show that the full-duplex link can realize alternative frequency output, and maintains good performance.

Choose the appropriate continuous function to describe the light field distribution of fusion biconical optical microfiber coupler which is made by a fusion tapering system. The weighted superposition of normalized triangular and rectangular distributions combine the weighted superposition of Gaussian and triangular distributions are used to achieve continuous changes in the mode field along the coupler region. The local mode coupling theory is used to derive the calculation formulas for the coupling coefficients of the optical microfiber coupler waist region and the tapered region near the waist region, and get the change curve of optical microfiber coupler output optical power with stretched length. Calculation results show that as the stretch length increases, the degree of light energy coupling back and forth alternately in both arms becomes smaller and appears envelope-like, until the coupling function of the waist region disappears. Among monitoring real-time data of the optical microfiber couplers′ output optical power, the effects of flame scan width and hydrogen flow on the length of two arms loss coupling effect are obtained. The flame scan width is wider, the uniform waist region is wider, the critical value of the stretch length is larger. The greater the hydrogen flow, the greater the melting degree, the smaller the critical value of the stretch length. The experimental results show that when the diameter of the fiber coupler reaches 1.6 μm, the coupling function disappears, the optical power of the two output ports is the same and constant, and the optical microfiber coupler has stable optical transmission characteristics.

To enforce the visual effect and vision quality of infrared polarization images, the infrared polarization image enhancement algorithm based on mutual structure regularization is proposed. Relying on the description of infrared polarization features, the spatial local weighted gradient fusion strategy of Q component and U component in Stokes parameters is presented, and the polarized feature image is obtained, describing the boundary and contour information. Then, the mutual structure regularization constraint scheme is put forward. The gradient magnitude similarity map is applied to jointly regularize the boundary structure similarity between enhanced result and polarized feature image, meanwhile regularize the radiation consistency between enhanced result and radiant intensity image. Finally, the enhanced infrared polarization image with high quality is optimized. Experiments demonstrate that our mutual structure regularization algorithm can boost the visual contrast, visibility, and the polarization saliency of artificial targets in complicated background, with high engineering computational reliability.

For the complex background of remote sensing images, the key objects in a scene image are small and large-scale variations, so that it needs to improve model representation ability for scene classification. Therefore, a deep multi-branch feature fusion network is proposed for remote sensing image scene classification. The multi-branch network structure is utilized to extract high-level, middle-level and low-level feature, and the three levels of features are then split-fused-aggregated into a grouped fusion. The fusion method is based on the proposed split-fusion-aggregation group fusion method. Finally, in order to pay attention to the loss of difficult to distinguish samples and labels, a loss function is proposed. The experimental results proved that the method proposed in this paper is very effective for improving the accuracy of classification. The accuracy rate on the UCM, AID, and OPTIMAL datasets surpasses other state-of-art algorithms. On the UCM dataset, 50% of the samples are trained, the accuracy rate is 99.29%, and the classification accuracy rate is increased by 1.35% compared with ARCNet-VGG16 algorithm. On the dataset AID, 50% of the samples are trained, and the accuracy rate is 95.56%, an increase of 0.98% compared with Two-Stream algorithm. 80% of the samples are trained on the dataset OPTIMAL, and the accuracy rate reached 95.43%, with an improvement of 2.73% compared with ARCNet-VGG16 algorithm.

Aiming at the problems of fuzzy reconstructed image and loss of high-frequency information caused by low sampling rate of multi-spectral filter array, sparse Raw data and so on, a new eight-spectral filter array distribution scheme is proposed, which is based on neighborhood gradient extension method to reconstruct the spectral Raw image. Firstly, based on the binary tree generation method, an eight-band filter distribution scheme with equal spatial probability ratio is designed in the 4×4 array of repetitive arrays. Then, for the sparse Raw image directly acquired by the sensor, the gradient information of sampling points in each spectrum segment is calculated. On the basis of maintaining the image structure features and texture information, the pixel value and gradient value of sampling points in the neighborhood are used to reconstruct the unsampled points, so as to obtain the complete spectral image information. Finally, based on the reconstructed eight-band spectral images, the pseudo- inverse matrix method is used to reconstruct the 31-band spectral values of each pixel position. The results show that compared with the mainstream image reconstruction methods, the proposed algorithm improves the peak signal-to-noise ratio and composite peak signal-to-noise ratio of reconstructed eight-band spectral images, reduces the mean square error of the spectrum, and better preserves the texture and edges of the image. Reduced artifacts such as color artifacts and image blur in multi-spectral filter array imaging.

In order to meet the detection requirement of aerial target in the complex background, according to the motion characteristic of aerial target in actual situation, the radiation characteristics of the target in different flight altitude and detection elevation were analyzed, the atmospheric radiation and attenuation data were calculated based on MODTRAN, and the infrared imaging simulation system was established based on the 3D model, the thermal radiation and reflection model of aircraft. Results shows that in mid-wavelength, the infrared radiation of the target plume is much stronger than that of the skin. In the long-wave band, the infrared radiation of the skin is stronger, and the corresponding simulation image has more details, the infrared imaging is still good, although infrared radiation of the plume is weakened. Under the same detection conditions, the higher the location, the thinner the atmosphere, so the detectable distance of the detector will become longer. The infrared radiation characterization and simulation system building can provide a reference for shortening the development time of infrared detector and further determining the detection spectrum and system solution.

The working process of aperture Scanning Near-Field Optical Microscopy (a-SNOM) under the illumination mode is simulated by using the finite element method of electromagnetic field. With changing the length and nanogap size of the optical resonant dipole antenna, the scanning curves of the radiative emission rate as a function of the central coordinate of the a-SNOM probe end surface are calculated. A superresolving measurement of the metallic nano-gap of the antenna beyond the aperture size of the a-SNOM probe is realized. For the a-SNOM probe with an aperture size of 100 nm, the smallest size of the antenna nanogap that can be resolved is 10 nm (0.016 times of the wavelength). By comparing the calculated results of the measured radiative emission rate of the a-SNOM probe for the metal and the dielectric dipole antennas, it is shown that the realization of the superresolving measurement of the metallic nanogap is due to the excitation of the gap surface plasmon polariton.

In order to provide a basis for the thermal control of the focusing telescope and the optimal design of the support structure, the three-dimensional full-size modeling and finite element analysis of the follow-up X-ray telescope′s mirrors group in the Einstein probe project are carried out. The influence of axial and radial temperature gradients, as well as the supported and unsupported structures on the deformation of the mirrors group is studied. The relationship between the surface error and the temperature difference is explored. The results show that the relation between the surface error and the mirrors′ radius for unsupported structures under the axial temperature gradient is close to the linear relation, while the relation under the radial temperature gradient is close to the piecewise quadratic relation. When the support structure is thermally deformed, the surface error corresponding to that occurs in the mirrors group. That transforms the in-phase roundness error into the out-of- phase roundness error, and increases the Peak-to-Valley value of the overall surface error of the mirrors group by 32.25%~123.01%, and the Root-Mean-Square value by 4.13%~5.14%. For supported structures, the thermally induced surface error is proportional to the temperature difference. When the temperature difference increases by 1℃, the Peak-to-Valley value and Root-Mean-Square value of surface error increase by 7.76 μm and 1.12 μm respectively under the axial temperature gradient, while 9.67 μm and 1.60 μm, respectively, under radial temperature gradient. The thermal-induced surface error of the focusing mirrors has a linear relationship with the mirrors size and temperature difference under certain conditions, and is significantly affected by the deformation of the support structure.

Based on the tunable diode laser absorption spectroscopy technology, a cloud water content detection system is developed in this paper. A 1 368.6 nm distributed feedback semiconductor laser was employed as detection light source, an orthogonal lock-in amplifier based on TLC7528 chip is designed, which improves the stability of measurement and the ability of restraining noise;The single board realizes the functions of laser driving, harmonic signal processing and concentration inversion. The system carries out on-line detection at different concentrations and temperatures, the experimental results show that the response time of the system is about 10 s, the error of water content is less than 5% in the range of 0~16 g/m3, and it can work normally under the condition of －55~+60℃. The device has the advantages of small size, high detection accuracy, fast response speed, and performance unaffected by temperature, which meets the needs of airborne cloud detection.

Process noise and photoelectric measurement noise seriously affect the sensitivity when detecting the displacement of the microsphere in the actual measurement. Aiming at this problem, a method of detecting the displacement of the microsphere based on Kalman filter is proposed. In order to obtain the displacement of the microsphere with high sensitivity and high signal-to-noise ratio, the harmonic oscillator model which interprets the motion of the microsphere is transformed into the form of state transition matrix for Kalman filter. Simulated results show that the root-mean-square error of measured displacement is reduced from 1 nm to 0.27 nm after filtered at 101 kPa. Experimental results show that the proposed method reduces the detection root-mean-square error of measured displacement from 2.8 nm to 1.1 nm at 293 K and 101 kPa. Other parameters remaining unchanged, the root mean square error is reduced from 5.2 nm to 2.1 nm at 293 K and 1 Pa. The proposed method can be applied to the laser cooling feedback scheme of the center-of-mass motion of a micro-particle optically trapped in high vacuum.

In order to realize the highly specific and sensitive detection for miRNA, a multiple miRNA quantitative detection protocol was designed by combined the fluorescence characteristics of quantum dots with the DNA shearing properties of double-strand specific nuclease. First, the two ends of the capture DNA are separately linked with the quantum dots and the ferroferric oxide magnetic nanoparticles to form a capture probe, and then the capture DNA and the detected miRNA will form a heteroduplex DNA-miRNA hybrid structure as they are complementary gene sequences. And then, the DNA is specifically sheared by double-strand specific nuclease to separate the quantum dots and the detected miRNA from the capture probe, and the isolated miRNA and the unpaired capture probe start a new round of hybridization and specific shear of the double-strand specific nuclease. Through the above cyclic process, quantum dots are continuously released from the capture probe, resulting in the continuous enhancement of the detected fluorescent signal, thereby achieving highly sensitive detection of tumor marker miRNA. The experimental results show that the specific quantitative detection of miRNA-141 and miRNA-1228 is successfully achieved by double-strand specific nuclease-assisted circular amplification of quantum dot fluorescence signals in the concentration range of 1 fmol/L to 100 pmol/L, and the detection limits reached 0.69 fmol/L and 0.21 fmol/L, respectively. In addition, compared with the real-time fluorescence quantitative polynucleotide chain reaction method, the proposed protocol obtains consistent detection results with a higher sensitivity.

Y3+/Pr3+ co-doped CaGdAlO4 phosphors were prepared by a self-propagating combustion method in combination with a subsequent heat treatment. The experimental results show that, when Gd3+ is replaced by Y3+, whose ion radius is close to that of Gd3+, the enhanced luminescence intensity of Pr3+ leads to a blue-shift of the maximum position of the absorption peak originating from the 4f-5d transition of Pr3+ from 261 nm to 259 nm. When the optimal concentrations of Y3+ and Pr3+ were determined to be 50% and 0.5%, respectively, Y3+/Pr3+/Yb3+co-doped CaGdAlO4 phosphors were further prepared, and their quantum cutting luminescence from deep ultraviolet to near-infrared was realized. As the Yb3+concentration reaches to 6%, the strongest luminescence of Yb3+ at 980 nm was observed. It is found that the calculated quantum cutting efficiency of Y3+/Pr3+/Yb3+ co-doped CaGdAlO4 phosphors is about 168%, which is higher than that of Pr3+/Yb3+ co-doped CaGdAlO4 phosphors. Moreover, under ultraviolet light (254 nm) irradiation, the strategy of substituting Y for Gd in the CaGdAlO4 host can inhibit the lattice thermalization in a certain extent. In a word, the replacement of Gd by cheap Y can lead to the reduced cost of the phosphors and the improved quantum cutting performance. This study has practical significance for developing and applying silicon space solar cells.

Aiming at the problem that the mask deformation due to its own gravity during the traditional contact exposure process, which can introduce nonnegligible linewidth errors and position errors, a set of high-precision fabrication methods for large-diameter quartz substrate diffractive lenses was proposed. A high-flatness and high-strength metal calibration fixture with vacuum channel on the back is adopted to attract the mask, and the pressure difference between the upper and lower surface of the mask is used to make it highly fit with the fixture to ensure the high flatness of the mask. Then the fixture is removed after all areas of the quartz substrate are in close contact with the structure surface of the mask. After the contact exposure and development are completed, the large-diameter quartz substrate is etched by reactive ion etching technology, and finally a high-precision micro-nano structure is obtained. The results of finite element analysis show that the deformation of the mask was reduced from 28.85 μm to 0.88 μm after using the calibration fixture. The experimental results show that the wave-front error of the 430mm two-step quartz substrate Fresnel diffraction lens prepared by this method is better than 1/25λ, the average diffraction efficiency is 38.24%, reaching 94.35% of the theoretical value, and it has well focusing and optical imaging effect.

Aiming at the problems of high dimension of hyperspectral image and low classification accuracy caused by non-linear classification between objects, a space spectrum classification algorithm based on multi-label shared subspace and kernel ridge regression is proposed.The inseparable features of similar pixels in linear space are mapped to high-dimensional space using kernel ridge regression, which realizes the effective separation of classification characteristics in high-dimensional space,so as to improve the accuracy of the similarity of features.At the same time,the high-dimensional sample data is mapped into the low-dimensional shared subspace.In the low- dimensional environment,the multi-class label is used as a guide,and the low-rank matrix is introduced to establish the prediction relationship between the category label and the shared space, and the common characteristics among the multiple labels are mined. Improve the use of common attributes among multiple categories to improve the classification accuracy of hyperspectral images.Finally,the singular value decomposition iteration method is used to solve the objective function,which can speed up the parameter solution to a certain extent.Simulation experiments are carried out on two sets of hyperspectral datasets, Indian pines and Pavia University,compared with other similar algorithms,the overall classification accuracy,average classification accuracy and kappa coefficient of this algorithm are improved by at least 4.76%,4.24% and 5.19% at low sample ratios.Compared with the non kernel algorithm,the overall classification accuracy,average classification accuracy and kappa coefficient of the algorithm are improved by at least 2.92%,2.8% and 3.48% without increasing the running time.

In August 2018, an on-orbit absolute radiometric calibration test for the thermal infrared channel of FY3D/MERSI-II satellite remote sensor was carried out at the Qinghai lake radiation correction test-site. The spectral radiance data of Qinghai Lake was obtained by means of fixed-point measurement. The sounding data were input to radioactive transfer model to compute the at-sensor radiance and brightness temperature of the satellite, and the calibration coefficients for thermal infrared channel 24 (10.26~11.26 μm) and channel 25 (11.50~12.50 μm) of FY3D/MERSI-II were calculated. AQUA/MODIS and NPP/VIIRS satellite remote sensors which have high calibration accuracy were used to evaluate the accuracy of the on-orbit radiometric calibration method. The average deviation of the channel brightness temperature is less than 0.5 K in the range of 10.26~11.26 μm and less than 1.0 K in the range of 11.50~12.50 μm, indicating that the on-orbit radiometric calibration method has better calibration accuracy, and the calibration results are reasonable and reliable. Comparing the on-orbit calibration results using the Qinghai Lake with the on-board calibration results, in the range of 10.26 ~ 11.26 μm and 11.50 ~ 12.50 μm, the average deviation of the channel brightness temperature is less than 0.5 K and 1.25 K, respectively. It shows that FY3D/MERSI-II runs stably on orbit. This test verified the FY3D/MERSI-II on-board calibration results, and provided a guarantee for the quantitative application of FY3D/MERSI-II remote sensing data.