Based on the thermal decomposition of nitrogen pentoxide (N2O5) and the thermal balance relationship between N2O5 and NO3 free radical, the concentrations of N2O5 and NO3 free radical are measured by cavity ring-down spectral technology. In view of the reversible balance between NO2 and N2O5, the influences of heating temperature and NO2 concentration on decomposition rate of N2O5 are investigated. Considering the loss of N2O5 in the measurement system, the inlet efficiency obtained by the preliminary quantitative analysis is about 88%. The optimum integration time is chosen according to the Allan variance, and the detection limit of volume fraction for the out-field observation is 8.6×10-12. Considering the uncertainty of the inlet efficiency, absorption cross section and incompletion thermal decomposition of N2O5, the estimated total measuring error is about ±10%. A practical detection experiment for nocturnal atmosphere is carried out in Hefei. The N2O5 concentration ranges from 3.5×10-11 to 1×10-9 with a average value of 4.52×10-10 during the measurement period. The proposed technique provides efficient way for realizing high sensivity on-line monitoring of N2O5 and NO3 free radical in ambient air.

The effective spin-rotational Hamiltonians of 2Σ12 and 2Π12 states of mercuric fluoride (202Hg19F) molecule are constructed, and the hyperfine structures, Stark shift in external electric field and Zeeman shift in external magnetic field of ground state are calculated. The variation of the g-factor in external electric field is simulated with the first-order perturbation theory. The possibility of using the N=1, J=1/2, F=1, MF=±1 state of 202Hg19F molecule to measure the electron electric dipole moment is discussed (N, J and F are quantum number of angular momentum).

When the beam is totally reflected on the interface between two media, the reflected light has a transverse Goos-H nchen (GH) shift. An atomic medium is introduced in the Kretschmann structure, and the surface plasmon wave is excited by the coupling light. The reflective GH shift of probe light under the surface plasmon assisted interference effect is studied. When the free propagating wave and the surface plasmon wave are respectively used as the coupling light, the reflectivity and the reflective GH shift of probe light are compared. It is shown that there is an asymmetric line-shape similar to Fano resonance in the reflectivity curve when the incident angle of the probe light deviates from the resonance angle, and the reflective GH shift can shift linearly between positive and negative values. When the coupling light is the surface plasmon wave, the reflective GH shift is more sensitive to the variation of the detuning of the probe beam.

A wide dynamic range linear measurement system of silicon detector is introduced. The system is based on flux addition, which controls the LEDs to turn on, off and the collector to collect data through time logic. In the adjustment range of LED injection current of 2.2×10-6-0.57 A, nearly nine orders linearity of silicon detector response current within the range of 3.92×10-11-10-2 A is calibrated. The experimental results show that the error introduced by the nonlinearity of the detector can reach 0.23% when the silicon detector is measuring in the dynamic range of nine orders and it is necessary to correct the measured value by the nonlinearity correction factor. In the end, a nonlinearity correction factor is given, ranging from 1 to 1.0023. The measurement uncertainty of the measurement results is analyzed, and the factors that affect the measurement accuracy of the system are listed. The influence of the spectral drift of the LED light source on the measurement accuracy of the system is analyzed quantitatively. The measurement uncertainties are 0.269%, 0.0116%, 0.00536% and 0.00320%, when the response current ranges of the silicon detector are 39.2 pA-0.326 nA, 0.326-81.6 nA, 81.6 nA-20.4 μA and 20.4 μA-10.2 mA respectively. The result shows that the system can be used in wide dynamic range response of high accuracy silicon detectors.

A phase noise compensation algorithm based on joint estimation of Kalman filtering (KF) in time and frequency domains is proposed aiming at higher-order quadrature amplitude modulation (QAM) based incoherent optical orthogonal frequency division multiplexing (CO-OFDM) system with large linewidth. Training symbols and pilot sequences in time domain are set in the transmitter. Frequency domain Kalman filtering is carried out based on training symbols at the receiver, and channel estimation value is obtained. Rough estimate value of phase noise is obtained with time domain extended Kalman filtering (EKF). The estimation value of phase noise in time domain is plural, and in order to obtain better compensation results, every OFDM symbol is divided into several sub-symbols according to the number of pilot sequences. Time domain EKF is carried out at the positions of pilot sequences. Rough estimation value of phase noise of every sampling point is obtained with linear interpolation at the last pilot of every sub-symbol. Predecision of frequency domain data after rough phase noise compensation and time domain phase noise fine compensation are carried out. Numerical simulation is performed by the proposed algorithm for CO-OFDM system with transmission rate of 50 Gbit·s-1 and transmission distance of 100 km. Results show that the compensation results achieved by the proposed method are better than that of other methods. When CO-OFDM system is with 16QAM and a laser linewidth of 1 MHz or with 32QAM and a laser linewidth of 800 kHz, bit error rate can reach the upper limit of forward error correction.

The acquisition of quadrature carriers is important for interferometric fiber-optic seismometer with heterodyne scheme. Harmonic distortion and relative amplitude error are the major parameters for quality evaluating. The existence of phase bias between quadrature carriers will lead to the harmonic distortion of demodulation result and increase the relative amplitude error. Relationship among phase bias of quadrature carriers, harmonic distortion and relative amplitude error is analyzed. Mathematical derivation is carried out with series decomposition and Bessel function expansion, and simulation verification is carried out. Analysis results show that the relative amplitude error and the harmonic distortion are both positively correlate with the phase bias of quadrature carriers. The phase bias should be controlled under 1.6×10-2 rad to ensure relative amplitude error lower than 1% and harmonic distortion better than -40 dB. A experimental system is established, and experiments are conducted. The experimental results are consistent with the theoretical results.

In order to reduce the working envelope size of multi-node laser communication antennas and improve the motion control accuracy of two-dimensional tip-tilt mirror, a compact mirror assembly is proposed. A scheme of directly bonding between a high volume fraction Al-based SiC (SiC/Al) supporter and a H-K9L plane mirror is adopted. The thermal stability of the tip-tilt mirror surface shape is improved, and the distance between the tip-tilt mirror assembly rotation center and the mirror surface is shortened to 20 mm. The design of three-point thin ring is used on the bonding surface. The influence of the bonding stress on the mirror surface is effectively reduced on the basis of ensuring the dynamic stiffness of the tip-tilt mirror assembly. The results of finite element analysis show that the fundamental frequency of the tip-tilt mirror assembly is 1319.96 Hz. The tip-tilt mirror surface shape peak-valley (PV) value is better than λ/4 (λ=632.8 nm) and the root mean square (RMS) value is better than λ/22 in the working temperature range of (20±5) ℃. A ZYGO laser interferometer is used for testing the mirror surface shape, and the test results show that the PV value of the tip-tilt mirror surface shape is better than λ/4 and the root mean square (RMS) value is better than λ/29 in the temperature range of (20±5) ℃. These results are better than tip-tilt mirror surface shape RMS value of λ/15 and meet the laser communication antenna requirement.

To solve the problem that the traditional electric-optical reconnaissance platform which is the exposed spherical structure increases the radar cross section of airplane dramatically, we propose a method using double reflectors rotating along the pitch axis and the azimuth axis to achieve wide-angle scanning. The conformal design with aircraft can be realized because of the small exposed size of this structure, and the cloaking performance of the aircraft is ensured. Based on the light reflection vector theory, we firstly study the imaging characteristics of the scanning system, and quantitatively analyze image rotation induced by the two reflectors rotating along the pitch axis and azimuth axis. The exact relationship between the degree and direction of the image rotation angle and the rotation angle and direction of the two reflectors is concluded. According to the above image rotation compensation theory, a bilateral control technique to eliminate the image rotation is put forward when the image de-rotation prism is controlled, and exactly cooperative motion of the scanning mirror and the de-rotation structure can be realized. Finally, imaging experiments are carried out to validate the proposed technique, and the results indicate that the image rotation is eliminated after de-rotation and high-precision optical image despun with root mean square less than 8' is achieved.

A phase-only encoding method based on one-dimensional grating function is proposed. Based on double-phase hologram encoding technique, the complex amplitude image is encoded into a phase-only image, and then the image is directly loaded into the spatial light modulator for image reconstruction. During the optical reconstruction, a 4-f system with a low pass filter is used to select the diffraction order, and the first order diffraction component is chosen for reconstruction. The one-dimensional grating encoding function can improve the energy of the first order diffraction component. The quality of the reconstructed images is increased because there is no interference from zero-order information of the phase element. The numerical and experimental results show that the encoded amplitude and phase of the complex object can be reconstructed effectively, and the power of the first order diffraction got from the proposed method is higher than that of two-dimensional checkboard encoding function.

Based on the sine/cosine (sin/cos) filtering technique, an adaptive filtering algorithm is proposed. This novel method can automatically select the filtering window size according to the fringe-orientation of the speckle phase fringe pattern. After calculating the fringe-orientation of the speckle wrapped phase fringe pattern, the filtering algorithm can choose an appropriate filtering window accordingly, and carry out adaptive mean filtering operations on sin and cos transformation maps of the speckle wrapped phase pattern, respectively. The wrapped phase fringe pattern is obtained by the four-quadrant arctangent function. Simulation and experimental results show that the proposed method can protect the stripe phase jump information effectively, and still be able to perform a good fringe filtering processing even for the speckle wrapped phase pattern with varying stripe density and complicated fringe shape. The filtered phase pattern is closer to the original stripe direction.

For the clearness of colored images captured by underwater image sensors, a lαβ color space image clearness algorithm is proposed. On the basis of former dark channel prior algorithm treatment on captured color images, the space mapping is used for further clearness processing, and changing RGB images to lαβ color space images. For the brightness channel l, the Tetrolet transform method is adopted. The bilateral filter is used to filter underwater image noise of high-frequency components, which contains most rough, edges, and other linear details. The nonlocal uniform filter is used to recover the clear low-frequency components, which contains the image’s most energy. Processed high-frequency and low-frequency images are inversely converted by Tetrolet transform to get recovered brightness channel image. The spatial mean color correction method is adopted to get recovered α and β channel images, and the processed brightness channel image and color channel images are inversely transformed to RGB space. Updating the transmissivity by input image to get clear color underwater image. Experimental results show that the proposed algorithm works well on underwater image restoration, and it is effective on the image color promotion and edge description.

Laser reflective tomography imaging is a new approach of long-range and high-resolution imaging. Reflective echo can be approximately considered as the adding noise convolution of transmitted pulse and target reflectance projection distribution. Hence, the broadening of transmitted pulse has significantly effect on resolution of reconstruction image. The existing filtering back-projection algorithm is insufficient to solve this problem effectively, while the pulse compression and deconvolution method can extract target reflectance distribution projection from echo, which will enhance the quality of reconstruction images. Based on the similarity of multi-angle detection, the blind deconvolution of one-dimensional echo signal is proposed based on multi-frame iterative approximation. Experiments are conducted on real laser radar, the reconstructed results show that the proposed method can significantly enhance the resolution and details of imaging, and give reference for the transmitted pulse.

As a widely used computational imaging method, the light field imaging's research is still limited to the visible band in the electromagnetic spectrum. Based on the camera array, a method of infrared light field imaging is proposed. A passive infrared camera is used to obtain the original infrared image sequences of the same static target at different positions of the same plane. The infrared light field database is built after translational parallax correction. Then resampling images are obtained based on the light field rendering theory. Compared with the traditional infrared imaging which only records the two-dimensional position information, the infrared field imaging can record four-dimensional information of the position and direction. Experimental results show that this method can obtain a resampling image with higher signal-to-noise ratio by blending multiple low signal-to-noise ratio images, realizing the imaging of the penetration barrier by the aperture superposition average and achieving the digital refocusing with different depths of infrared scenes by resampling different depth values selected. The proposed method can make the infrared imaging more valuable in military and civilian fields.

Horizontal light field three-dimensional (3D) display is an important 3D display method, it can achieve fairly good 3D display effect when remarkably compressing the mass information of light rays that need to be processed. As there is no change in vertical light field, its expressive force of display definition and the ability of monocular focusing for horizontal light field are both different from the ideal light field. The point spread function (PSF) of the horizontal light field is analyzed based on the scanning light field display. Based on the auto-focusing principle of human eye and camera, the horizontal light field that is reconstructed under different display parameters is focusing simulated, which shows that the effect of horizontal scattering angle of light and the image number per screen spinning circle of the projection on the monocular focusing ability in horizontal light field is obtained. The conclusion is verified by using a scanning horizontal light field display prototype. And the results show that the maximum focusing height of horizontal light field declines with the increasing of horizontal diffusing angle of light ray, and it goes up with the increasing of the image number per screen spinning circle of the projection. The proposed analytical method and the conclusion can provide the design consideration for the horizontal light field display system of monocular focusing.

When the surface tiny defects are illuminated by the light with different wavelengths, their optical image exist nonlinear and amplified distortion phenomenon with different degrees. It has certain effects on target extraction and signal-to-noise ratio (SNR) of the imaging information. An approach that defect image illuminated by red, green, and blue light source is used for dynamic spectral coding imaging is proposed. The image synthesis with high redundancy can be realized through pixel-level image fusion. Then it can further enhance SNR while fetching rich details of micro defects on the surface. The spectral coding theory is analyzed based on three-primary-color images, and then the dynamic weight fusion imaging method is proposed based on the image gradient. The corresponding noise analysis model of spectral nonlinear amplified signal is given. The effectiveness of dynamic weight fusion reducing standard deviation is fully verified by both theoretical analysis and numerical simulation. In the bright field surface defect imaging experiment, color complementary metal oxide silicon (CMOS) camera of three-primary-color equilibrium response is adopted to obtain three-primary-color filtering image of single micron-size defect point on the surface. By comparing with the results of traditional edge extraction, non-dynamic weight combination, and other methods, it is proved that the proposed optimization method can get a high SNR image with richer details. In the dark field surface defect imaging experiment, image gray level mean gradient and extracted defect quantity as evaluation parameters, namely two aspects of optimizing image quality and defect recognition ability, are used to futher verify the effectiveness of high fidelity and low noise. The study of this dynamic spectral coding fusion imaging method can effectively reduce the noises from spectral nonlinear amplification.

A high-performance polarization independent reflector based on a multilayered grating structure with multi-subpart profile is discussed. Owing to the advantages of co-existence and interaction of TE polarization light and TM polarization light leaky modes, the proposed reflector can offer combined merits of high reflectivity (over 97%), wide angular bandwidth (about 24.6°), low insertion loss (below 0.25 dB) and low polarization dependent loss (below 0.18 dB) over a broadband spectrum of 1.65-1.72 μm. The rigorous coupled wave analysis method is used to verify the good process tolerance of the reflector in the existing process error range.

The mechanism and the effect of microstructure evolution on the surface microhardness of TC6 titanium alloys after laser peening (LP) are studied. The results show that both of the surface microhardness and the residual stress of materials after LP increase with the increase of the power density, and the depths of the microhardness effect layer and the residual stress effect layer caused by LP also increase with the increase of the power density, and the depths are 500-600 μm. The effect mechanism of LP on the microhardness of TC6 titanium alloys consists of the fine grain strengthening and the dislocation strengthening. The number of large and small angle grain boundaries increases because of the grain refinement and the grain boundary can prevent the materials to yield. High density dislocations produced by LP can improve the yield strength of materials, hinder the movement of dislocations and restrain the crack initiation, which can improve the mechanical property of materials.

An automatic frequency stabilization system of external cavity diode laser based on digital signal processing (DSP) technology is achieved. The automatic frequency stabilization system uses saturated absorption spectroscopy of rubidium atom as the frequency reference and obtains error signal by modulation and demodulation technology. The system continuously collects saturated absorption signal and error signal by analog-to-digital converter at a fixed rate, the collected digital signal is treated and analyzed by DSP chip. The DSP chip controls the switch of modulation signal by its general purpose input output, and realizes the control of laser frequency scanning and digital feedback outputting by digital-to-analog converter. The laser frequency stabilization technology can not only stabilize the frequency of external cavity diode laser automatically, but also relock laser frequency in time after losing lock by evaluating the lock state of laser in real time, which improves the long-time running ability of the laser. Finally, the laser that uses the laser frequency stabilization technology is applied to a prototype of cold atomic clock in space, and it can meet the needs of relevant scientific experiments.

Based on the comprehensive analysis of laser kinetics and hydrodynamic processes of alkali vapor laser amplifiers and combined with the thermal effect, saturation amplification effect, amplified spontaneous emission, and high level excitation and ionization, a comparatively ideal physical model is established to simulate the output characteristics of diode-pumped alkali vapor laser amplifiers under flow and heat dissipation conditions. The influence of gas flow velocity on output power is simulated with two different flow modes in longitudinal and transverse directions. The variation trend of the particle number density at high pumping power density is compared and analyzed. Finally, the effect of the power distribution ratio of the amplifier in each stage on the improvement of cascade amplifier output power is simulated. Results show that under the same operating temperature condition, multiple equal-length steam pools and equal distribution of pumping power allow high-level amplifiers to achieve higher magnification than that of low-level amplifiers. Thus, the model contributes to the parametric selection and optimization of the design of alkali vapor laser amplifiers.

In high power solid laser facility, the hot images are an important physical mechanism in damaging the optical components. The hot image property induced by defects in nonlinear propagation is analyzed theoretically. The phase defect key spectrum method of hot image extracted by band-pass imaging technology is proposed. The typical 16 phase defects are constructed to analyze the quantitative relationship between hot image property and band-pass imaging property with three optical types, and the linear relationship between hot image intensity and relative brightness of band-pass image are proposed. It shows that the correlation coefficient is connected with the optical type and band-pass filter parameters. The results have great significance for hot images and lay a technique foundation for phase defects detection in high power laser systems.

The influences of defocus dispersion and propagation time delay, which are caused by the chromatic aberration in cascade large-diameter spatial filters, on the ultra-short pulse shape and the temporal contrast are investigated. The relationship among beam diameter, chromatic aberration, pulse shape distortion and temporal contrast degradation in both near and far fields is quantitatively analyzed by the numerical simulation. From the perspective of pulse shape and temporal contrast, the tolerance range of residual chromatic aberration from large-diameter spatial filters after achromatism is given, which provides a theoretical foundation for the design and optimization of spatial filters in a high power ultra-short pulsed laser system.

The camera lens distortion often causes image distortion during damage monitoring process of large structures, great errors will be resulted and damage detection accuracy will be reduced if the distorted image is directly used for calibration and measurement. We propose an improved non-metric distortion calibration method based on straight line characteristics to correct the distortion effectively. Firstly, we analyze the aberration model of the distorted image in actual measurement. Then, we obtain the constraint relationships with weighting factors based on the principle of linear projective invariance and three-point approximate collinearity according to the straight line features in the scene, and establish two sets of distortion correction constraint equations to solve the distortion parameters. Finally, the feasibility and validity of the proposed method is demonstrated experimentally. Root mean square error of the proposed method is improved by 0.21 pixel compared with the calibration method based on the linear feature without weighting factors.

Linear array camera is often used for the moving objects imaging because of the characteristics of high sensitivity, high pixel resolution, and wide dynamic range. In the dynamic detection of running fault image of the multiple units train, the images will stretch or compress in the direction of the train, because the train is not running at an ideal speed through the linear array camera. The number of images taken by the same train at different times is inconsistent, which brings challenges to automatic positioning, identification and automatic fault detection. In order to solve the unaligned problem, we present an block-based image registration method. The image is firstly divided into many sub-blocks, and then feature extraction, matching, and quantization. Each sub-block is corrected in accordance to the pixel distance of feature points. Finally, the correction of the entire images is fulfilled by concatenating the corrected sub-blocks, and the alignment of the target images with the standard image is completed. The experimental result demonstrates that this method has a better performance on alignment for multiple units train sequence images captured by linear array camera. It can accurately positioning the target in the sequence image.

The aim of extrinsic parameter calibration is to build the relationship between vision coordinate system and extrinsic standard coordinate system. The substitutable target sphere for vision-measurement is designed to cooperate the vision-measurement and instrument measurement. The vision-measurement target sphere and the equipment-measurement target sphere replace each other to get the coordinate of common points in both vision coordinate and standard coordinate. And the extrinsic parameters are solved by optimizing the target function with the coordinate of common points in both systems using non-linear optimization method. The design of substitutable vision-measurement target sphere consists of target, light source and sphere shell to satisfy the substitutability with equipment-measurement target sphere and the availability of center of sphere. The propagation of error during the calibration is presented. The accuracy of calibration is promoted through simulation and verified by experiment. The result shows that the accuracy reaches 0.036 mm, which shows that the proposed method can realize public point data acquisition directly, flexibly and high-accuracyly.

A novel ellipse classification and relative pose estimation algorithm is presented based on surface of revolution (SOR) for multiple-ellipse images. Firstly, the contour following method is performed on images to detect ellipses. Secondly, the meaningful ellipses are obtained based on parallel constraint and vertical constraint. Finally, relative pose between the target and the camera is calculated by the meaningful ellipses. Experimental results indicate that the method performs well in ellipse classification and pose estimation. The precision of classification is higher than 97% for synthetic images corrupted by 0-16% salt-and-pepper noise. The absolute error of the pose angle is less than 1°, and the absolute errors along the depth direction and other directions are less than 80 mm and 15 mm, respectively, when the measurement distance is less than 10 m.

In order to improve the robustness of visual target tracking algorithm, a multiple feature fusion tracking algorithm is proposed based on covariance matrix. Under the framework of quantum genetic algorithm, the region covariance descriptor is used to fuse color, edge, and texture features. A fast covariance intersection algorithm is adopted to update the model. The proposed algorithm makes the most use of low dimension of the region covariance descriptor, fast convergence and strong global search ability of the quantum genetic algorithm, and fast calculation ability of the fast covariance intersection algorithm, which greatly improves the efficiency of fusing, matching and updating process, and effectively realizes fast and efficient multi-feature fusion tracking. Experimental results show that the proposed algorithm can effectively cope with the interference, such as occlusion, rotation, deformation and motion blur, and achieve fast and robust target tracking.

A portable non-mydriatic fundus camera with 40° field of view is designed, and it can be used to capture retinal images. The optical system of this camera consists of lighting system and imaging system, in which the lighting system is equipped with visible light source and infrared focusing source. The use of infrared light source focusing can avoid the use of drugs on eye mydriatic treatment. The light source uses a unique circular LED and it is imaged on the human eye pupil to avoid reflection effect as it falls on the cornea. Focusing lens is placed in the imaging system, which has ±15D diopter compensation function. In imaging system, the root mean square of spot diagrams is less than 2.8 μm, the field curvature is less than 0.2 mm, the distortion is less than 0.6%, and the modulation transfer function values are higher than 0.4 at 70 lp/mm in all fields. The original image is clearly reproduced on the image plane by using Zemax software for imaging simulation. This camera can be used for the prevention and rehabilitation of disease in ophthalmic medical industry.

A novel mathematical model which converts the solar collection problem into a nonlinear boundary problem for the elliptic type Monge-Ampére equations based on differential geometry, refraction law, reflection law and the conservation of energy is proposed. A freeform solar concentrator is designed based on this mathematical model. The freeform concentrator system is simulated by ray-tracing software. The results indicate that considering the Fresnel loss and the absorption of optical materials, when the sunlight possesses 0.27° divergence half-angle, the geometric concentration ratio and the focusing efficiency of the 1000 mm freeform solar concentrator reach 500 and 77.5%, respectively. The freeform designed by this method has higher degree of freedom, which makes it possible to design solar concentrators with different degrees of concentrating requirements.

The structure of the new double asymmetric liquid crystal lens is improved on the basis of the single round hole electrode liquid crystal lens. Combined with geometrical optics and liquid crystal theory, Zemax is used to simulate and optimize the parameters of this double layer structure liquid crystal lens. Zemax analysis results show that in the same low drive voltage( in the range of 2.5Vrms to 20Vrms) and at the angle of view with 0°, 3.5°and 5°, the double layer structure lens has wider focusing range than the single layer structure lens. The short focal length reduces from 19.6172 mm to 9.9059 mm. The aberration is significantly reduced. When the optical modulation transfer function (MTF) is 0.6, the radial direction resolution increases from 12.06 lp/mm to 21.02 lp/mm, almost doubled. The image resolution and clarity are significantly improved. The high frequency part MTF increases from 0.1 to 0.3. Finally, the experiment verifies that the diffraction specular of the double layer structure liquid crystal lens is the smallest at 20Vrms.

Based on the equivalent circuit of nanodipole, combine the multi-layer waveguide and resonator structure, a nano-metamaterial solar absorber with high absorptivity and broadband is designed. The unit structure of the absorber is composed of a double hexagonal metamaterial nanocolumnar and a silicon ring, in which the silicon ring is fitted with eight miniature Au nanocolumns. The finite difference time domain method is used to analyze the absorption characteristics of the metamaterial solar absorber in broadband, different-polarized incident light and large-angle incident light. The numerical analysis shows that the absorption band of the absorber is mainly concentrated at 400-1500 nm, and the average absorption rate can reach 94%. The incident light of different polarization states has little effect on the absorptivity of the absorber and the average absorptivity of the absorber can reach 90% at a big incidence angle of ±60°. The high absorptivity of the broadband of the absorber is attributed to the synergetic effect of the slow-wave effect and localized surface plasmon resonance.

Organic-inorganic hybrid perovskite has been attracted increasing attention in perovskite light-emitting diodes (PeLEDs) and lasers. How to improve the luminous efficiency of perovskite film is a hot topic. Gold nanoparticles (Au NPs) with diameter of 20 nm are doped into PEDOT∶PSS. The emission intensity of CH3NH3PbBr3 film increases 2.7-fold when the CH3NH3PbBr3 film is used as the luminescent layer. The results show that, the absorption of CH3NH3PbBr3 film and the radiation transition rate of excitons are improved when Au NPs are introduced. The results of the analysis combined with optical simulation show that the near-field and far-field surface plasmons of Au NPs can both coupling with absorption and emission areas of perovskite film, and the maximize luminous efficiency can be obtained. The luminous efficiency of perovskite film can be improved at the greatest extent by comprehensive surface plasmons of Au NPs in near field and far field, which can provide important theoretical direction and technical support in the fabrications of high efficiency PeLEDs and lasers.

Based on the transmission characteristics of surface plasma sub-wavelength structure, a metal-dielectric-metal waveguide coupled ring cavity structure with metallic double-slit is proposed. The Fano resonance is formed by the coupled destructive interference between wide wave with continuous state generated by a metallic double-slit waveguide resonator and narrow wave with isolated state generated by a ring cavity. According to the coupled wave theory, the transmission and phase characteristics of Fano resonance formed by this structure are analyzed. The finite element analysis method is used to simulate the structure, and the effects of the structural parameters on the slow light effect are analyzed quantitatively to optimize the structural parameters. The results show that the optimized group index can reach 205. This structure can provide an effective theoretical reference for the design of integrated plasma slow light devices.

A ray-tracing algorithm of the elliptical reflection zone plate (ERZP) based on the grating diffraction theory is proposed, and the diffractive focusing and spectrally resolved properties of an ERZP are analyzed. Based on the proposed algorithm, the ERZP ray-tracing module is added in the optical simulation software X-LAB, which makes it possess the advantages of small computational cost and high efficiency. This is of great significance to the design and numerical simulation of optical systems with an ERZP.

A quantum private communication system based on the wavelength-mode division co-multiplexing is put forward and designed. The basic principle of wavelength-mode division co-multiplexing is introduced. The transmission experiment is performed for 10 times with the system model built by Optisystem. The time domain waveform and spectra of signals are obtained and analyzed. Stabilities of wavelength and linear polarization mode of signals in the transmission are tested. The quantum key distribution based on the scheme of double unbalanced Mach-Zehnder interferometers is realized in the system. The error bit rate, eye diagram and quality factor of classical optical data are obtained. The results show that this quantum private communication system converges the advantages of two multiplexing forms. The channel capacity is broadened, and the isolation and the orthogonality between signals are enhanced. In addition, the nonlinear effects and the crosstalk between signals are reduced efficiently, and the quantum signal is well maintained in the coexisting transmission process of quantum-classical signals. The proposed quantum private communication system is confirmed to be effective and applicable.

Body of water is a kind of important content of synthetic aperture radar (SAR) image interpretation. In this paper, a registration method, which is based on the contours and aiming at the imaging features of SAR image including body of water, is proposed. At first, an adaptive weighting Markov random field (MRF) segmentation model which is integrating local statistical information of observed image is proposed to segment the target of water body of SAR image and accurately extract its contour. Then, a non-uniform Gaussian mixture model (GMM) of contour matching is proposed. The mixture model can integrate both the location information of point of contours and the gray scale similarity information of windows including the contour points as the centers. At last, the registration experiments of SAR image including body of water are conducted. Results show that the proposed MRF segmentation model can accurately locate the edge of object and reserve the details of image. The non-uniform GMM for contours matching is robust to noise, outliers and local deformation, which can achieve the registration of SAR image including body of water better.

The calculation of the shifts between sub-images in extended scene Shack-Hartmann wavefront sensor is one of the key factors affecting the accuracy of wavefront sensing, which is commonly achieved by correlation algorithm and it can attain sub-pixel precision through methods such as parabolic interpolation algorithm. The calculation can also be achieved by using the centroid of the correlation function. The main step is first calculating the correlation function between two sub-images and then calculating the centroid of the correlation function, which achieves sub-pixel precision. Based on simulation, the measurement accuracy of this method is related to the size of the sub-image, the window size of the correlation function in the calculation of the centroid and threshold of the correlation function. Besides, the signal-to-noise ratio of the image also effects the accuracy of the calculation. Studies show that, when the signal-to-noise ratio of the image is less than 1, the error of the centroid algorithm is relatively large. When the signal-to-noise ratio of the image is larger than 2, the error of the centroid-of-correlation-function approach is only half of that of the parabolic interpolation. The experimental results are in good agreement with the simulation results.

Using modified Dobson dielectric constant model as the basic model, we analyze and validate the relationships between soil volumetric water content or soil salinity and dielectric constant. On this basis, we analyze the relationship between backscattering coefficient and dielectric constant by extracting the backscattering coefficient of the radar image at different polarization modes. The results show that the volumetric water content and soil salinity are the main influencing factors of dielectric constant of the soil. The volumetric water content is the decisive factor of the real part of the dielectric constant, and it determines the value of the real part of the dielectric constant. The imaginary part of the dielectric constant is affected by various factors, and the soil salinity is the main factor. The interaction between volumetric water content and soil salinity affects the backscattering coefficient. At the cross polarization mode, the dielectric constant is the main factor affecting the backscattering coefficient of the radar image. The dielectric constant of the soil has a certain potential in monitoring the soil salinity and volumetric water content. It is entirely possible to retrieve soil salinity by radar images.

This study aims to detect the size and attribute of particles simultaneously by extracting nonlinear eigenvector of size and attribute in light scattering signals and using general regression neural network (GRNN).The scattering signals are decomposed by the method of empirical mode decomposition (EMD), and the three-dimensional energy distribution is extracted. Sample entropies of three kinds of particles with same attribute and different sizes are calculated. It is found that the sample entropy can identify the attribute of particles. In order to eliminate the influence of particle size and attribute on the scattering, the Hilbert transform is used for the light scattering signals, and time-frequency domain eigenvectors are extracted, which form a high-dimensional eigenvectors set together with the sample entropy. The eigenvectors set is summed up into six eigenvectors by the local linear embedding (LLE) algorithm and used as the input layer of the GRNN to identify the particle size and attribute. Finally, an experiment is conducted to test the 0.11 μm SiO2 particles, 2 μm and 4 μm polystyrene pellets. The results show that the accuracy of particle size detection and attribute recognition exceeds 90%.

Three Raman characteristic peaks of sodium benzoate located in 843.5 cm-1, 1007 cm-1 and 1605 cm-1 are identified by using self-built Raman spectroscopy detection system. Using silver colloidal prepared by reduction of silver nitrate with sodium citrate as surface enhancer, we develop a rapid detection method for sodium benzoate in commercial carbonated beverage. The surface enhanced Raman spectra of 44 carbonated beverage samples with different sodium benzoate concentrations are randomly divided into 32 calibration sets and 12 validation sets, and all Raman spectra are carried out the pretreatments of Savitzky-Golay smoothing and baseline removal of fluorescence background. Simple linear regression analysis method, multiple linear regression analysis method, partial least squares regression analysis method, principal component regression analysis method and support vector machine regression analysis method are used to build models. The results show that the optimal model is binary linear regression analysis model based on the sodium benzoate characteristic peaks at Raman shift of 843.5 cm-1 and 1605 cm-1. In the binary linear regression model, correlation coefficient of validation set is 0.9603, root mean square error of validation set is 0.0867×10-3. The rapid and quantitative detection of sodium benzoate in commercial carbonated beverages can be realized by the binary linear regression analysis model, and this provides technical support for the real-time online detection of the content of sodium benzoate in food.

The two-line method is usually used to measure the temperature and mole fraction of gases simultaneously in tunable diode laser absorption spectroscopy. However, in practical applications of the two-line method, there exists some limitations such as cross-talk in the frequency division multiplexing method or reducing temporal resolution in the time division multiplexing method. To solve this problem, a new calibration-free one-line method based on wavelength modulation spectroscopy is proposed to implement simultaneous measurement of gas temperature and mole fraction by using a single absorption line. Using main combustion product CO2 as the target gas, and selecting R(50) spectrum line of CO2 at central frequency of 5007.787 cm-1, we verify the calibration-free one-line method. The temperature is extracted from line shape of the background subtracted peak normalized second harmonic signal, and mole faction of CO2 is extracted from the background subtracted first harmonic normalized second harmonic signal. The experimental results show that the maximum relative error between temperature from the calibration-free one-line method and measured temperature is less than 2.5%, and the maximum relative error of mole fraction is less than 2.8%. It is feasible to measure the temperature and mole fraction of CO2 at the same time using the calibration-free one-line method.

The wavelength modulation method in tunable diode laser absorption spectroscopy is widely used in the measurement of gas concentration due to its advantages of adapting to harsh environment and high sensitivity. Compared with the common sine wave modulation, the triangular modulation has higher sensitivity. However, the triangular modulation method is generally combined with the calibration approach to measure gas concentration. In this study, a new calibration-free method based on triangular wave modulation is proposed and a frequency response model of distributed feedback laser is developed. The experimental results illustrate that the relative residual of etalon signal is less than 0.4% and the relative residual of the first harmonic normalized second harmonic signal is less than 1.2%, which prove the feasibility of the proposed model. The calibration-free measurement of CH4 gas concentration based on triangular wave modulation is realized.

Aluminium (Al) thin films are prepared on the quartz substrate, and meanwhile Al nanoparticles are obtained by baking the Al thin films. The absorption property of Al nanoparticles with different thicknesses are studied. The results show that the roughness of Al thin films increases with the increase of baking temperature. When the baking temperature reaches 300 ℃, the Al thin films are completely transformed into Al nanoparticles. When the film thickness varies from 5 nm to 25 nm, the redshift of the thin film resonance absorption peak is 40 nm at the baking temperature of 300 ℃. This fabrication process of Al nanoparticles is simple, time-saving, low-cost, and high-efficiency.

Spectral reflectance reconstruction from a single RGB image of a trichromatic digital camera not only can effectively avoid the pixel distortion between the imaging channels existing in spectrum imaging system based on optical bandpass filters, but also can save the capturing time and acquire the spectral images with high spatial resolution. However, the spectral reconstruction error is influenced by reconstruction methods. A new spectral reconstruction method based on camera response expansion and local inverse distance weighted optimization is proposed. Using CIEDE2000 color difference and spectral root-mean-square error as the evaluated metrics, we use Canon 600D digital camera to verify the proposed method, and compare the proposed method with current advanced methods. The results show that the proposed method outperforms the several existing advanced methods, and average CIEDE2000 color difference and average spectral root-mean-square error of the proposed method decrease to 1.0389 and 0.0230, respectively.