In order to detect the characteristics of refractive index of the oil mixed kerosene and diesel, the sensitive features of refractive index of long period fiber grating were analyzed by using the coupled-mode theory, the relationship between the content of diesel oil and the long period fiber grating’s resonant wavelength and transmitted intensity was obtained. The result shows that when the diesel oil of the mixed oil increases, the long period fiber grating resonance wavelength blue-shifts. And when the concentration of diesel oil reaches a certain concentration that the refractive index of the solution is equal to the cladding refractive index, the resonance wavelength will shift to the maximum. As the concentration of diesel changes 1%, the average shifts of resonance wavelength reaches 0.622 7 nm. As the diesel oil increases sequentially, the refractive index of mixed oil exceeds the cladding refractive index, and the resonant wavelength does not change basically, the shape changes greatly with the bandwidth decreasing and the peak loss increasing. And with the concentration of diesel oil increasing unceasingly, the peak loss increase and bandwidth diminishes. As the concentration of diesel changes 1%, the peak loss reaches 0.154 6 dB. So the long period fiber grating has a potential application prospect in the detection of mixed fuel concentration.

An practical few-mode fiber with elliptical pure SiO2 core was designed for large-capacity optical communication systems. The design principle and reference standard are presented, and the transmission properties were analyzed with full vector finite element method combined with perfectly matched layer boundary conditions. At the wavelength of 1.4~1.65 μm, the fiber is in stable dual-mode operation with modes HE11 and HE21, and the effective refractive index difference between the modes is greater than 1.8×10-3, which can avoid the mode coupling and crosstalk. At the wavelength of 1.55 μm, the chromatic dispersion of the modes HE11 and HE21 is 19.61 and 4.41 ps/(nm·km) respectively, the dispersion slope is 0.048 and 0.002 ps/(nm2·km) respectively, the mode field area is 97.17 and 143.96 μm2 respectively, and the attenuation coefficient of each mode is less than 0.21 dB/km. Transmission properties of the fiber can basically meet the G.652 and G.655 fiber standards, and it can be made by the existing mature “preform drawing” technology. This is significant for the promotion of next generation communication network bandwidth, which can be combined with WDM technologies to increase optical network transmission capacities exponentially.

In order to adapt to the seepage pressure monitoring′s need of the mine and the dam,a kind of fiber Bragg grating seepage pressure sensor based on the combination of the piston and the diamond structure was proposed. The piston passes the test pressure to the diamond structure and the diamond structure pulls elastic steel sheet, leading the center wavelength of the fiber Bragg grating bonded on the elastic steel sheet to change. In the 500 kPa test environment, the stress characteristics of the diamond structure were analyzed by using the finite element method when the vertex angle was respectively 90°, 110°, 130° and 150°. According to the simulation parameters, the seepage pressure sensor was developed and pressure calibration test and temperature compensation test were carried out on the sensor. Experimental results show that, the sensitivity of the sensor to the seepage pressure is 2.04 nm/MPa、the fitting degree is 0.997 and the repeatability is 0.9%. The temperature sensitivity of pressure measuring grating is 0.023 33 nm/℃ and 0.021 68 nm/℃ respectively, and the temperature compensation grating is 0.009 916 nm/℃.

To solve the problem that fluid-structure coupling mode makes the frequency band of hydrophone narrowed, the influence of fluid on the natural frequency of the distributed feedback fiber laser hydrophone with two diaphragms was theoretically analyzed. Based on the finite element software, the mode and frequency response performance of the hydrophone in the air and fluid before and after the reinforcement were simulated. Prototypes of the hydrophone were fabricated and tested. The results show that response curve of the hydrophone before reinforcement fluctuates greatly due to the existence of several natural frequencies in a frequency range of 2 500~8 000 Hz. The average acoustic pressure sensitivity of the hydrophone reaches -142.77±0.8 dB after reinforcement, which verifies the influence of fluid on the frequency response performance of the hydrophone and the effectiveness of the measures. It agrees well with both the theoretical analysis and simulation results.

Combining Pseudo-inverse Ghost Imaging (PGI) with iterative denoising of ghost imaging, a pseudo-inverse iterative method was proposed for object reconstruction of ghost imaging. This method employed the reconstructed results of PGI as the initial values and selected an appropriate threshold value correlated to the noise interference. It also used iterative operation to approach the actual noise interference, and enhanced the Peak Signal to Noise Ratio (PSNR) of the reconstructed images by suppressing the noise in the end. By using PSNR and correlation coefficient (CC) as the yardstick, the reconstructed results of Pseudo-inverse Iterative Ghost Imaging (PIGI) were compared and analyzed with those of Differential Ghost Imaging (DGI) and PGI. The simulation experiment results show that the PSNR of the pseudo-inverse iterative method is about 1.0 dB and 3.1 dB higher than those of PGI and DGI respectively, and it′s CC and visual effects are also improved compared with PGI and DGI, which verify the validity of this method.

In order to rapidly detect the space debris in the Geosynchronous Earth Orbit (GEO) image with optical observation, a grading detecting method based on Signal-to-noise Ratio(SNR) was proposed. First, the real measured data are analyzed, and the characteristics that image velocity of different GEO debris are same is acquired. An improved dynamic programming method is proposed based on the velocity information obtained from high SNR debris, which can detect low SNR debris effectively. The results of real image show that the detection performance of the grading detecting method is the best when the search window of recursive equation is 5 pixel×5 pixel, and the detection time is reduced by more than 87% as compared with that of original algorithm when the cumulative number is greater than 5. With the advantages of high detection rate, low false alarm rate and low computational cost, the proposed method is suitable for the detection of space debris in GEO optical observation images.

For suppressing the error from the incident angle fluctuation during laser thickness measurement online, the principles of laser transmission and reflection thickness measurement were analyzed by geometrical optics, which show that when the fluctuation of laser incident angle is nearby a particular value, the thickness measurement errors of two methods are complementary with one positive and the other negative. On this basis, a complementary thickness measurement method was proposed based on laser transmission and reflection simultaneous measurement, and the error could be limited between the transmission type and reflection type measurement errors, suppressing the online thickness measurement error. For the polymethyl methacrylate sheet, theoretical calculation results show that when the fluctuation span of the incident angle is at 67.013±4 degrees, the relative error absolute value is within 1% and the mean error suppression ratio is greater than 90%. When the incident angle is 61.536 degrees, the error suppression ratio is 100%. Using one line structured light laser and two linear array CCD cameras, a complementary thickness measurement system was set up. The polymethyl methacrylate sheets with the nominal thickness of 1~5 mm were measured. In addition to the 1mm glass, the complementary thickness measurement error is restrained between the transmission and reflection measurement errors, and the maximum error suppression ratio is 61%. Experimental results show that the complementary method can effectively restrain the error and improve the online thickness measurement accuracy.

Low-level precision boundary information of the unknown surface is useful for digital sensor path planning, data segmentation and feature recognition in reverse engineering. In order to acquire the low-level boundary information of the measured surface both rapidly and easily, the Coaxial Stereo Vision Photogrammetry (CSVP) was systematically studied. The mathematical model of CSVP was established, the influences of system parameters including the focal length of the cameras, the baseline distance and the spatial position of the measured points on measuring accuracy were analyzed, and the mathematical analysis for determining the optimum range of the baseline distance of the two cameras was carried out. In addition, the characteristics of the CSVP epipolar geometry were studied. Then a new approach for rapid digitization of surface boundaries based on CSVP was proposed. This approach was characterized by an integrated use of a Coordinate Measuring Machine (CMM) and a single CCD camera, the CMM was employed to provide an accurate and repeatable platform for the camera. Consequently, the camera can be located at any predefined position within the CMM’s working volume. This enables the camera to get stereo image pairs in different positions along the same axis, which can only be achieved by two cameras without the CMM. During data processing, the characteristics of the CSVP epipolar geometry, in which the corresponding epipolar lines in the front and back image planes are arranged parallel to each other, and the epipolar lines pass through the main points of their own image planes respectively, were applied to facilitate stereo matching, by which the surface boundary information of the measured surface can be obtained both rapidly and easily compare to conventional binocular stereo vision method. Experimental results indicate that the average error of the surface boundaries reconstructed by the data gathered by the proposed method is 0.268 mm. It can meet the accuracy requirements of low-level boundary information in reverse engineering.

The generation mechanism of the laser beat frequency was studied by using chirped fiber Bragg grating as an example,and a model was established to realize the dispersion measurement of chirped fiber Bragg grating. The system structure and measuring principle are detailed demonstrated. The measurement results and the theoretical values are analyzed and compared,as a result, they are in good consistency. The accuracy of the dispersion measurement reaches to 0.1 ps at the spectrum analyzer resolution of 2.5 kHz. The dispersion measurement of chirped fiber Bragg grating confirms the feasibility of the system, at the same time, the system is relatively simple and highly accuracy. So it is expected to provide reference for the dispersion measurement.

The theoretical results of the oscillated threshold for dual-wavelength, continue-wave Yb∶YAG laser were presented, and then its output was experimentally investigated. In our experiment setup, a plane-concave cavity was employed for laser oscillating by end-pumping with a 940nm fiber coupling laser diode. A Yb∶YAG crystal was taken as the laser crystal in the cavity. The single wavelength and dual-wavelength laser were respectively obtained by using the Output Coupling (OC) of 10%, 15%, and 20%. At the highest pump power of 20W, the maximum output power at 1 050 nm is 3.94 W at the OC of 10% and the maximum output power at 1 030 nm is 3.40 W at the OC of 20%. The corresponding optical to optical conversion efficiencies are 19.7% and 17.0%, respectively. At the output coupling of 15%, the dual-wavelength output power of 0.79 W was obtained at the pump power of 11.7 W, corresponding to an optical-to-optical conversion efficiency of 6.8%. It is experimentally found that the output power ratio P1 030 nm/P1 050 nm was about 1∶1.3. The central wavelengths of the dual-wavelength laser were located at 1 030.31 nm and 1 047.50 nm by using a grating spectrometer. At an output power at 1 030 nm of 3.0 W, its output power stability of RMS is determined to be better than 0.18% in a 30 min operation. The proposed model gives results that agree fairly well with the experimental data. Our results suggest that high efficient, compact stable Yb-doping dual-wavelength lasers can be designed from our model.

The orientation effect for Below-Threshold Harmonics (BTHs) from H2+ was studied through the numerical simulations. With excluding the contributions of excited states successively, the orientation dependence of BTHs, obtained with the driving laser wavelength of 760 nm, was analyzed in detail. The research results show that the complex orientation dependence of BTHs parallel and perpendicular to the laser polarization is closely related to the resonance effect between the ground state and the neighboring excited states, where the axis symmetry of these excited states play an important role. A simple model which contains the transition dipole is used to explain these complex orientation-related phenomena. The main results are checked with using the first excited state as the initial evolution state. The results can give suggestions on relevant experimental studies of orientation dependence of BTHs.

The biased LED illuminated light pipe angle segmentation and its virtual image array forming principle were reserached. The light pipe size was calculated according to the biased LED position and divergence angles, and then optimizated with front imaging lens, intermediate image polarization conversion system, backend integral lens and polarization beam splitter. The polarization conversion system structure was determined by the optimized intermediate image distribution to insure the polarization conversion of luminous energy within the range of LED divergence angle and realize the uniform illumination to color-filter liquid crystal on siliconsize. A color-filter liquid crystal on silicon projection optical engine was finally designed with the white LED, wich can output light flux of 12.8 lumens per watt(the LED efficiency is about 114 lm/W) with 93% irradiance uniformity. Comparing with the optical engine without polarization conversion, the proposed optical engine enhances the light efficiency of the color-filter liquid crystal on silicon micro-projection system and enriches the light pipe applications while maintaining the homogeneity.

In order to study the effects of tunnel illumination for visibility under low transmission, and to provide the theoretical basis for tunnel illumination brightness adjustment under low permeability conditions, two cameras with different spectral characteristics were used to be detectors for obtaining the relationship of observation transmittance, lighting levels, the target/background contrast. The results show that the target/background contrast increases with the increase of lighting luminance, there is nonlinear relationship between the two; the maximum value of the target/background contrast that can be achieved is limited by transmission; Improving the target/background contrast and the visibility by increasing lighting luminance can only be effective in a certain brightness range. According to the experiments it is concluded that improving lighting brightness has little effect on visibility under the condition of high lighting level, under the condition of low lighting level, improving the lighting luminance can effectively improve visibility. The lighting luminance should be adjusted in proportion on the base of the concentration of smoke and transmission in order to ensure visibility and driving safety.

Taking a SiC mirror with an aperture of 500mm for example, the supporting characteristic of rear support in centre was studied based on spercific lightweight shape and supporting structure by using finite element analysis, and the effects of structural parameters on the performance were analyzed. The analyses point out that the optimal proportion of the diameter of support hole to the aperture of mirror is 0.23, the optimal rear shape of mirror with different aperture should be determined by using optimization method, and the surface accuracy can be improved by increasing the support depth when the gravity in radial direction. The analyses of supporting structure indicate that the radius of bolt circle at the bottom of the flexible connector is the key factor which has great influence on both the surface accuracy under the load case of temperature variation and the first order frequency of mirror subassembly, so it is considerable to weigh the requirment of surface accuracy and structural basic frequency when chosing the optimal value of the radius. The surface accuracy of the mirror supported by rear in centre is less affected by the assembling stress from outside and not sensitive to notch depth changing. The support length has a great influence on dynamic stiffness of the structure and its decrease will increase the first order frequency of mirror subassembly. Finally the maximum aperture of the space SiC mirror supported by rear in centre is intended to be 750 mm, which means that the mirror supported by rear in centre without of structural constraint can be satisfied with the refered requirment when its aperture is less than 750 mm.

In the view of the present problem that the microlens array of high F-number (more than 10) is difficult to be manufactured, this paper proposed a new fabrication method for it. Firstly, A photoresist layer with high viscosity was spin-coated evenly on a microlens array fabricated by melting photoresist and etching technology. Under the viscosity of photoresist and the surface tension of photoresist in curing process, the F-number of microlens array increased observably. Compared with the traditional processing method, this fabrication method is very simple and the surface profile of microlens array is very good. In addition, microlens arrays with different F-number could be obtained with the viscosity of photoresist was adjusted. Based on the method, a microlens array with F-number up to 40 was fabricated. The experimental results show that the profile of the microlens array is good enough to verify the feasibility of the fabrication method.

Calibrating the quantum efficiency of the single-photon detector by correlated photon pairs is quite important for improving the radiometric calibration precision of optical load. Using a continuous wave (355 nm) laser to pump BBO crystal to generate type-I spontaneous parametric down conversion, the quantum efficiency of the single-photon detector at 736 nm was measured for the collinear and nonlinear phase matching modes respectively. Results show that, the combined standard uncertainty of calibration result for the collinear and nonlinear modes is 0.71% and 0.39% respectively, the relative deviation is better than 0.4%. and the quantum efficiency of the single-photon detector can be calibrated for the two phase matching modes with an excellent consistence. At the last, the characteristics of the collinear and nonlinear modes was compared. The research provides the basis of choosing crystal phase matching mode for the calibration of remote sensor by correlated photon pairs in the future.

The quasi-periodic structures of Fibonacci sequence composed of conventional materials were proposed, and their spatial transmittance properties were investigated by using the transfer matrix method. The corresponding low-pass spatial filters with a small angle-domain bandwidth were designed based on these good spatial transmittance properties. The numerical simulation results show that, the angle-domain bandwidth can be tuned by changing the structure types and sequence numbers, and the angle-domain bandwidth of the filters becomes smaller and smaller with the increase of the sequence number or m value of Fibonacci sequence F(m,1). On the basis of the above regulation, the accurate adjustment can be made by changing the refractive-index parameter of the quasi-periodic structures. Compared to the former Metamaterial spatial filters with a small angle-domain bandwidth, the spatial filters based on Fibonacci quasi-periodic structures are more simple to be made and more likely to be applied to a new generation of high-power laser system.

The Poly(3,4-ethylenedioxythiophene)∶Poly(styrenesulfonate) (PEDOT∶PSS)films modified by the method of Dimethyl Sulfoxide (DMSO) was directly spin-coated on the PEDOT∶PSS anode interface layer, which made the performance of perovskite solar cells device has been greatly improved. Under the DMSO spin-coating speed of 5000 rpm, the power conversion efficiency of the device has reached up to 11.43%, which increases 29.15% compared with the device with an unmodified PEDOT∶PSS anode interface layer. The transmission spectra, surface morphology, conductivity of the PEDOT∶PSS films before and after modification were tested, and the external quantum efficiency curve and the J-V characteristic curve under illumination and dark were also tested to reveal the origin of the improvement of the device performance. The results show that, the conductivity of the modified PEDOT∶PSS film has been improved significantly, and thus the anode of the device can more efficiently extract and collect the charge carriers of holes. Compared with the device with unmodified PEDOT∶PSS, the short circuit current density of the modified device has been enlarged significantly that accounts for the higher power conversion efficiency.

The master equation of the density operator in the system of atom interacting with thermal reservoir was concisely solved by virtue of Ket-Bra entangled state. Analytical solution expression of the master equation was given. Considering that each of atoms interacts with thermal reservoir respectively, negativity was adopted to quantify the degree of tripartite entanglement among three atoms, and properties of tripartite entanglement among atoms were investigated. The influences of mean photon of the thermal reservoir and atomic spontaneous emission rate on properties of tripartite entanglement were discussed by using the numerical method. The results show that the tripartite entanglement among atoms decays accelerating with the increase of mean photon of the thermal reservoir and atomic spontaneous emission rate.

By using the multi-angle dynamic light scattering measurement and the weighted constrained regularization method, the four groups simulated particle systems with bimodal distribution(100/600 nm, 200/600 nm, 300/600 nm, 350/600 nm) were measured by selecting one, three, six and ten scattering angles respectively. The results of inversion of size distribution show that, by using the weighted constrained regularization method to inverse the multi-angle dynamic light scattering data of the particle systems with bimodal distribution, the bimodal particle size distributions with a peak position ratio less than 2∶1 and containing large particles(>350 nm) can be attained. This conclusion was verified by the measurement results of the standard polystyrene latex particles. The reason to attain the bimodal particle size distributions of the large particles is that, the multi-angle dynamic light scattering can provide more particle size information of large particles, the weighted constrained regularization inversion method can reduce the noise of the measurement data. Therefore, the weighted inversion of the multi-angle dynamic light scattering measurement data can achieve the measurement of the bimodal particle systems with a peak position ratio less than 2∶1 and containing large particles.

In order to realize the rapid and high precision calibration of standard scattering plate used in calibrating visibility meter, based on the calibration principle which a standard scattering plate calibrates a forward scattering visibility meter, an error analysis method for the optical system of the standard scattering plate calibration system used in a calibration visibility meter was established. The working principles of the calibration system were analyzed, and subsequently, a model of this optical system was established with a combination of the deviation arising from its optical system, fabrication and adjustment. Further, an experiment was designed to validate the model’s correctness. Next, the main errors that affect the precision of the scattering plate’s optical system were analyzed, for which an error propagation model was constructed. Finally, a comprehensive error analysis method for the system is proposed and a comprehensive deviation model is developed according to the analysis of the deviation of distortion, image plane position, principal point position, image plane inclination, and focal length. Each deviation is analyzed respectively, and the allowable deviation range of the deviation of distortion, image plane position, principal point position, image plane inclination, and focal length are, in order, 0.024 mm, 0.399 mm, 0.02 mm, 0.28 rad and 0.392 mm. Consequently, there is theoretical basis for precision improvement of the calibration system and the error sources analysis and compensation during calibration.

According to the needs of the detection of fluorescence with low concentration and short lifetime in the OH radical measurement based on fluorescence assay by gas expansion, a gated photon counting technique for resonance fluorescence detection was described, which was actualized by designing a nanosecond gating circuit applied to photomultiplier. Fluorescence was detected by a high gain 13-stage end-window photomultiplier, whose gating was actualized by changing the voltage of the photomultiplier dynodes. The circuit could obtain stable modulation voltage, with a 168 ns delay time and a 20 ns rising time. After optimizing the components and matching parameters of gating circuit, the radio frequency noise introduced by the circuit could be reduced in 210 ns and the on/off extinction could be up to 105 by switching the voltage applied to the first, third and fifth dynode of the photomultiplier. The gating system was applied to the fluorescence assay by gas expansion system for fluorescence detection and the OH radical fluorescence signal was obtained. The excitation spectrum of OH radical was measured in the wavelength range of 307.8~308.2 nm. Experiments show that the proposed gating technique can be used to suppress the influence of laser stray light, and detect the OH radical fluorescence signal in a particular time sequence.

When the Tunable Diode Laser Absorption Spectroscopy (TDLAS) analyzer is used to measure the hydrogen sulfide in nature gas, there are strong interferences from light hydrocarbon and CO2 in the natural gas background. Their spectra structure is imposed on the analyze spectra. The spectral interferences affect the extraction of the H2S absorption spectrum. The Partial Least Squares(PLS) algorithm is proposed to deal with the spectral interferences. The Common Least Square (CLS) and the PLS models are adopted in analyzer to evaluate the differential spectrum and direct measurement spectrum of 0~50 ppm H2S in natural gas. PLS is superior than CLS in the analysis of both differential spectrum and direct spectrum. Based the analyzer reading, the absolute error of PLS result with direct measurement spectrum is within ±1 ppm. With PLS algorithm, the analyzer need not to store the mass data of reference spectra, and the complicated differential system can be elimentated from analyzer, which can save the cost and improve robustness and the time response.