The scintillation caused by the atmosphere turbulence and strong background noise from sunlight and other lighting equipment are two main problems in visible light communication (VLC) atmosphere transmission system. In order to overcome the channel fading effect caused by the atmosphere turbulence and the noise interference caused by the strong background light, VLC atmosphere channel with strong background noise is modeled. Diversity receiving technologies are utilized to improve the bit error rate (BER) performance of the system at the same transmitting power. According to the channel model, outdoor long-distance VLC system based on intensity detection pulse position modulation (PPM) in turbulence atmosphere channel using diversity receiving technologies is finally set up. In our simulation, the system bandwidth is 400 MHz and bit rate is 800 Mb/s. The BER performances of three diversity receiving technologies: maximal ratio combing (MRC), equal gain combing (EGC), selection combing (SC) are also compared. The results show that under the same transmitting power, the improvement of BER performance by MRC is the best, followed by EGC and SC is poor. Taking 7% forward error correction(FEC) as the BER threshold, the required LED transmitting power is greatly decreased with MRC. Furthermore, with the increase of the number of diversity branches, the BER performance is better.

When the vortex beam propagates through the turbulent atmosphere, the random variations will be produced in the amplitude and phase of the beam. And the intensity fluctuations and spread of the radiation pattern will be induced at the observation plane. some results about the vortex beams broadening are obtained by numerical modeling using four-dimension code when the vortex beams propagate through the turbulent atmosphere under different conditions. The vortex beams are the lower order Laguerre-Gaussian modes. The results indicate that if the propagation distance is longer or the turbulence is stronger, the beam broadened by the turbulence will be more severe. And if the topological charge is higher, or the beam′s waist width is narrower, or the wavelength is longer, the beam broadened by the turbulence will be smaller. Though the inner scale and the outer scale of turbulence have an effect on the beam broadening, the influence of them is relatively weak. In addition, the broadening of vortex beam and fundamental Gauss beam through the turbulent atmosphere are compared numerically.

For adaptive optics with curvature sensor, two close-loop wavefront control techniques those based on direct fitting method and Laplacian eigenfunctions method are comparative analyzed. The basic principles of two methods are analyzed, and then a numerical simulation model of 36-element curvature adaptive optics is setup and simulations of atmospheric turbulence wavefront aberration correction are carried out. The results show that, comparing with the direct fitting method, the stability and correction accuracy of Laplacian eigenfunctions method are obvious better when the proper modes are chosen, and the stability and accuracy of the direct fitting method are significantly worse when the phase distortion is larger.

Space debris detection using superconducting nanowire single-photon detector (SSPD) as detectors is proposed and both theoretically and equivalent experimentally verified. The multi-detection characteristic of SSPD during gating period is analyzed, and the signal noise ratio (SNR) model with echo photon number is established. Effects of laser repetition rate, sky background noise rate and dark count rate of SSPD on SNR are discussed. Taking the kHz laser ranging system of Yunnan Observatories as an example, combined with the echo photon number equation, it implies that the kHz laser ranging system at Yunnan Observatories has the capability for 1 m2 space debris detection from 830 km away. Considering the fiber coupling requirement, an experimental curve of SNR versus echo number is obtained, which verifies the proposed method. Both theoretical and experimental results show that SSPD has the potential for space debris laser ranging.

Aiming at the big difference between theoretical and battlefield detection ability of airborne photoelectric system and the inadequacy of operation ability, the spatial distribution function of target reflective background radiation is obtained and the quantitative method is given. The target original radiation is studied and the models of level and pitch radiation intensity envelope are built. Considering the various operational factors, the equations of detection ability in level and pitching angle are given. The concept of detection probability envelope is put forward, and the relationship between operating range and detection probability is obtained and the envelope probability characteristic of airborne photoelectric system is analyzed quantitatively. The simulation results show that detection envelope changes with the change of target speed，azimuth and pitching angle. When meeting the demands of false alarm probability and signal noise ratio, the detection probability envelope has optimum detection point, which provides theoretical reference for developing the detection performance of airborne photoelectric system.

Fiber Bragg gratings (FBGs) are inscribed in both H2-loaded and H2-free fiber using 800 nm femtosecond laser, 244 nm Ar+ laser and a phase mask. The regeneration of three kinds of FBGs is observed in different processing temperatures. The models of regeneration process as well as regeneration temperature versus time are established. The FBGs regeneration temperature thresholds are defined. Experimental results and model analysis show that the regeneration temperature thresholds of femtosecond FBG written in H2-free fiber, femtosecond FBG written in H2- free fiber and ultraviolet (UV) FBG in H2- loaded fiber are around 888 ℃ , 780 ℃ and 770 ℃ , respectively. The regenerated FBGs in H2-loaded fiber decay in case of high temperature, while regenerated femtosecond FBG in H2-free fiber has well temperature stability.

A novel optical fiber Fabry- Perot pressure sensor using a corrugated diaphragm is presented. The mechanical model of corrugated diaphragm is analyzed and the parameters are optimized by simulation. The structures of the sensor and the production methods are elaborated. Pressure tests are carried out by employing the micro-pressure sensor testing system. Experimental results demonstrate that the sensor has reasonable linearity, sensitivity and repeatability in the range of 0 to 0.1 MPa.

A scheme of equalizing the uneven pulse amplitude from a rational harmonic mode-locked laser is proposed and verified, in which an optical fiber active ring filter is employed. The active ring filter is a comb filter with tunable free spectral range, which can select the mode-locked component and suppress other harmonics and super-modes by carefully tuning the optical delay line in it. This process is able to effectively balance the pulse amplitude. Theoretically, the simulation is performed to compare the waveform and radio frequency spectrum before and after filtering. The results show that the active ring filter can effectively filter the expected frequency, and the higher the Q is, the better the amplitude equalizationisis. In the experiment, the 7th, 11th, 14th mode-locked pulses are verified respectively and mode-suppression ratio can be improved by more than 20 dB.

To enhance the security level and practicality of optical validation technique, an optical multiple-level security validation method is proposed based on the multiplexing of orthogonal polarization states in threedimensional space. Two phase-only masks are generated by adopting the designed multiple diffractive planes and multiple signal windows phase retrieval algorithm, in order to reproduce Fresnel diffraction field with all of the subblocks which are obtained by the partition of the validated image distributed in specific locations in threedimensional space. One of the two phase-only masks is taken as the system lock. The other one is acted as the security validation key. The two phase-only masks are illuminated by orthogonal polarized respectively. The control of both intensity distributions and polarization distributions in different place are achieved in three-dimensional space. Only when both the security validation key and the three-dimensional orthogonal polarization map key are obtained, the validated image is retrieved. The correlation coefficients between the verification image and simulation or experimental results are 0.93 and 0.79 respectively, which shows the proposed system is a quite compact setup, with both high security level and multiple-level validation functionality.orthogonal polarization multiplexing

An improved and rapid three dimensional Gerchberg-Saxton (GS) algorithm based on the classic GS algorithm for computer generated holograms is proposed and applied to holographic optical tweezers. Theoretical simulations and experimental results have demonstrated the rapidity and efficiency of the proposed algorithm. A robust holographic optical tweezers setup based on phase-only liquid-crystal spatial light modulator(SLM) is built, and stable trapping and dynamic manipulation of yeast cells and silica beads with large array traps in three dimensions are demonstrated. Two special traps, i.e., line trap with intensity gradient distribution and optical vortex trap, are generated to transport and rotate micro-particles respectively. The system is verified to be robust on particles manipulations, which provides a new and powerful tool for researches on biology, colloid physics and so on.

In order to study the influence of targets with various polarization properties on resolution of active polarization imaging system, an experimental polarization imaging system with LED source is designed. The optical elements with high polarization extinction ratio are placed before the LED source and imaging devices. Two targets with different surface polarization properties are applied in the system. The image of imaging system for underwater environment is obtained. The experimental images are processed with inclined edge method and the modulation transfer function (MTF) is extracted. Comparing MTF results in various experimental environments using orthogonal imaging and polarization difference imaging, the conclusion is obtained that polarization technique is beneficial to suppress the forward scattered light and enhance resolution of the system. For different targets, the proper processes are applied to obtain high resolution images. Meanwhile, the conclusion is appropriate for both of linear and circular polarization illuminations.

X-ray imaging technology has developed fast in spatial explorations. In order to obtain higher throughput and larger effective area, Wolter-Ⅰnested telescope structure is usually adopted to focus and image the spatial Xray sources. Traditional optical analysis software is imperfect in the analysis of grazing incident system. Therefore, programs are written using the MT_RAYOR tools to evaluate the image quality of Wolter X-ray nested telescope. MT_RAYOR has an advantage of being general, accurate, convenient and fast in predicting grazing incident Wolter- Ⅰnested structures. Based on MT_RAYOR, the structure parameters of nested conical telescope working at 0.2~ 20 keV are designed, and detailed image quality analysis are presented, including the effective area, point spread function, and encircled energy function. The system can achieve a stable effective area of about 500 cm2 at 0.2~10 keV, and the effective area keeps above 250 cm2 in hard X-ray region, thus, the system has a wide range of working wavelength and good stability. Furthermore, the spokes and surface deformation profile are taken into consideration in order to evaluate the effects on image quality. The results have directive significance to optimization and assembling of the telescope system.

A new method for obtaining 3D shape and texture information of objects is proposed. A digital projector is used to project the two encoding color phase-shifted grating projection onto the object surface. Extracting R, G, B three primary colors, fringe patterns and background light containing object height and texture information are obtained. The three-dimensional morphology of the object is reconstructed by using the improved 2+1 phaseshift algorithm for fringe patterns containing the object height information. Object texture information is obtained by colour coding using the background light. Texture mapping technique is used to restore the texture of the object. Computer simulation and experimental results show the validity and feasibility of the proposed method.

The phase modulation and demodulation of double beam interferometer often use ellipse fitting to calculate relevant parameters, and a method is developed to assess calculation precisions of these parameters. The maximum deviations of parameters calculated by ellipse fitting should be computed in different levels of noise according to adaptive Monte Carlo method; then the precisions of fitted parameters can be estimated according to the noise floor of interference signal which is measured in experiments. The algorithm of fiber-optic hydrophone based on 3×3 coupler using two interference signals is analyzed as an example, and the relationship between the parameter value and device properties needs to be studied in order to improve the demodulation effect of hydrophone. As a result, the precisions of parameters calculated by ellipse fitting in experiments should be assessed firstly. The assessment method of precisions is applied to hydrophone experiments, and the noise floor of measured interference signal is close to -70 dB·V2/Hz from 20 Hz to 4 kHz. The deviations of parameters are less than 0.06% and 0.08° according to adaptive Monte Carlo method.

In order to improve the resolution of the laser Doppler vibrometer (LDV) and measure surface microvibration, an LDV equipped with a dual-frequency ring laser is proposed. The source and optical path structure of the system are introduced, and the measurement principle is derived. The dual-frequency ring laser, modified by a multioscillator ring laser gyroscope with stable frequency difference and narrow linewidth, can emit two beams in two directions and the two beams show a certain angle and have a fixed frequency difference. Combined with the grating technology, the surface transverse microvibration measurement can be realized. Compared with other LDV, the system has simple optical path and high resolution, and the maximum noise of amplitude resolution is lower than 0.012 μm·Hz1/ 2 in the laboratory experiment.

According to the discrepancy between the measured polarization information obtained from polarization remote sensing detection and the real polarization information, the measuring accuracy of the polarimatric bidirectional reflectance distribution function (BRDF), the polarization degree and the polarization phase angle can be affected by three system error sources in polarization remote imaging system, which is discussed. The error analysis model of polarization remote sensing detection is established. The influence of polarizer angle positioning error on measuring Stokes parameters is analyzed, and the influence of polarizer angle orientation on polarization detection accuracy is numerically simulated; based on the feature space interval of polarization remote sensing detection and the resolution ratio of the imaging CCD, the influence of the visual field space coincidence error on BRDF is discussed; then the influence of photon noise of imaging system and other inherent systematic errors on polarization detection results is analyzed. According to error transfer principle, the measuring errors caused by three error sources are compounded, and the general error model with respect to linear polarization degree and polarization phase angle is derived. Experiments show the error model of polarization remote sensing detection can truly reflect the influence of polarization detection system error sources on measuring accuracy of BRDF.

A model for wave-front distortions is built up based on the random phase screen, and the wave-front is fitted by Zernike polynomials with different orders. By comparing and analyzing the power spectrum density (PSD) of the original wave-front and the fitted one, the correspomding relationship between the used orders of Zernike polynomials and the spatial frequency of the wave- front is obtained. Consequently, the insufficient of the conventional method for fitting high frequency phase by Zernike polynomials is revealed, and the local fitting method based on Zernike polynomials is further proposed. In this improvement method, the residual wave-front in the conventional fitting way is decomposed into many subdomains fitted by Zernike polynomials individually. The results indicate that, in the conventional fitting way, the range of spatial frequency of the wave-front that can be accurately described by Zernike polynomials increases gradually with the fitting order of Zernike polynomials, but the increment is modest; even fitted by Zernike polynomials with much higher order, it’s difficult to describe the high frequency components of the wave-front accurately. However, the spatial frequency of wave-front accurately described by Zernike polynomials obviously increases by using the local fitting way. In order to increase the fitting accuracy, increasing the number of subdomains is more superior than increasing the number of the used orders of Zernike polynomials. For the number of subdomains in the local fitting way is fixed, increasing the used orders of Zernike polynomials in subdomains makes more precise fit than increasing the number of overall fitted orders.

In order to obtain uniform white light beam of high luminance, a kind of homogenized beam combination system is designed based on fly-eye lenses, the light sources consist of red, green and blue semiconductor lasers. There are two fly-eye lenses modules in the optical path, the first one is used to generate uniform white light spot, while the second one is used to transform the white light spot into spatially uniform white beam. The optical tracing software is used to simulate the optical path, and the luminance and color uniformity of light distribution at different locations in space are analyzed. The simulation results show that uniform white light beam is obtained, and the feasibility of the optical system is verified theoretically. The experimental facility is set up, and the color spectrometer is used to measure the combined white beam at the distances of 1, 2, 5 m. The test results show that the illumination uniformity is greater than 90%, and color coordinate standard deviation is less than 0.0027. The uniform white light beam combined by this optical path can be widely applied to medical phototherapy, display and automotive lighting, with the advantages of high luminance and uniformity in color coordinates and spatial intensity.

In terms of underwater non-parallel binocular image matching not being parallel correction, and no longer satisfying the epipolar constraint in the air, a kind of epipolar constraint model that suitable for underwater is presented. According to the differences of relative position between the camera and waterproof cover, the underwater imaging ways of binocular vision is divided into parallel imaging, common reflection surface imaging and independent reflection surface imaging. And the epipolar constraint model of the last two are deduced. The camera is calibrated. The scale invariant feature transform (SIFT) algorithm can help to match stereo. And corresponding curve of the feature points on reference image is derived. According to whether the corresponding feature is on the curve, the false matching points are eliminated and the matching accuracy are improved. Experimental results show that the underwater curve constraint model can effectively eliminate false matching points, and reduce the error matching rate.

(Eu0.045Li3xLuy)2O3 nanocrystals are prepared by the precipitation method. The X-ray diffraction, Fourier transform infrared spectra, scanning electron microscopic images and transmission electron microscopic images are used to analyze the microstructure and morphology of the nanocrystals. To analyze the luminescence properties, the excitation spectra, emission spectra and luminescence decay curves of the samples are measured. The influence of precipitation agent, solvent, temperature, annealing condition and other factors on the microstructure, luminescence properties, fluorescence decay and energy level lifetime for (Eu0.045Li3xLuy)2O3 nanocrystals is researched. The results show that the luminous intensity of the (Eu0.045Li3x=0.015Luy=0.94)2O3 nanocrystals precipitated in ammonia by adding lithium carbonate into the precursor powder and after calcination in activated carbon at 1000 ℃ increases by about twice compared with the sample which is prepared without lithium carbonate added, and increases by about four times compared with the sample calcined in air at 800 ℃.

Using the nanophosphors, X-ray luminescence computed tomography (XLCT) is proposed as a new molecular imaging modality that provides functional and molecular imaging capability. The reconstruction for the nanophosphors sample distribution is an ill-posed problem due to the strong scattering of photons in biological tissues. So accurate and stable reconstruction of nanophosphors distribution remains a challenging problem. In order to solve the problem, the diffusion approximation model is chosen to describe the photon transfer process, and the split augmented Lagrangian shrinkage algorithm based on L1 regularization is used for reconstruction. In the numerical simulations and physical experiments, the new method exhibits better performance in imaging quality and convergence rate compared with primal augmented Lagrangian method.

In order to investigate the human emotional state recognition, the functional near-infrared spectroscopy (fNIRs) technique is applied to measure hemodynamic signals of 15 participants who are requested to see six types of pictures, and the participants have to complete 7-point rating scale of valence and arousal after every picture stimulus. The support vector machine (SVM) and support vector machine based recursive feature elimination (SVMRFE) algorithm are applied to design classifiers. Under different emotional image stimulus, the hemodynamic signals of some participants show significant neural response. With the target classification based on valence, arousal and emotion category, the accuracy is 81%, 78.78% and 68%, respectively. The 5th and 6th channels for fNIRs measurement are significantly sensitive to arousal and valence state, and the two channels are located at orbitonfrontal cortex and dorsolateral prefrontal cortex regions. Besides, it is found that the entropy of fNIRs can reflect the variation in emotional state effectively. The results suggest that fNIRs can be used for recognition of human emotional state.功能状态等方面的研究。

The assumption that biological tissues are semi-infinite in the longitudinal direction and infinite in the transverse direction is applied in traditional diffusion equations. Aiming at the biological tissues, e.g. forearms and fingers, that are not infinite in the transverse direction, a diffusion model for random multi- layer rectangular biological tissues is established. It is assumed that biological tissues are semi-infinite and multi-layered in the longitudinal direction, and are rectangular in the transverse direction. Under the rectangular boundary conditions, exact solution of the diffusion equation for light in semi-infinite multi-layer rectangular media in steady-state is provided based on the diffusion equation of light propagating in biological media and by combining with the extrapolated boundary conditions. The spatially resolved diffusion is calculated using the established model, and corresponding Monte Carlo simulation is programmed to demonstrate correctness of the equation. The established equation does not only solve the problem of rectangular media in the transverse direction, but also the problem of media that are infinite in the transverse direction and semi-infinite in the longitudinal direction, even the problem of tissues that are infinite in the transverse x or y axial direction and finite in the other axial direction.

Mid-infrared supercontinuum generation is demonstrated by using a 75 % germanium-doped silica fiber pumped by a 2 μm Q- switched thulium- doped fiber laser with pulse width of 50 ns. The free space coupling efficiency from the pump laser to the germanium-doped fiber is enhanced by fusion-splicing a 100~200 μm long multimode fiber. Length of germanium-doped fiber is optimized. Broadband supercontinuum generation ranging from 1.9 μm to 2.9 μm with 10 dB and 20 dB bandwidths of 950 nm and 980 nm, respectively. The 2.9 μm long wavelength limit is close to the record reported so far for highly germanium-doped fiber based supercontinuum generation sources.

A method is proposed to determine the carrier envelope phase (CEP) for few-cycle laser pulses based on the asymmetry of the angular distributions of high- energy photoelectrons. The dependence of angular distributions of high-energy photoelectron for high-order above threshold ionization of helium in few-cycle laser pulses in the tunneling regime is investigated by using the second-order strong field approximation. By choosing the energy range in the photoelectron distributions appropriately, the dependence of the asymmetry parameter on the CEP can be obtained. Experimental results show that the change of the asymmetry parameter with the CEP obtained in the present work has the same trend with that from solving the time-dependent Schrodinger equation (TDSE). While in the TDSE calculations the contributions from the low energy photoelectrons are included, the asymmetry parameters obtained in the present work only account for the high-energy photoelectrons. Therefore, the proposed method provides a more convenient way for experimental determination of laser carrier phase.

To meet the requirement of large-field, low-distortion and small-volume for optical system used in remote sensing field, a large-field freeform four-mirror off-axis reflective imaging system is designed with the 3D construction method, which is with the field of view of 60° and the relative aperture of 1/14. In this paper, the 3D construction method is introduced. A freeform optical system can be obtained directly from a starting point of conic system with the 3D construction method, and it can be taken as a good starting point for further optimization. In the final system, the average of the modulation transform function (MTF) of all field of view is greater than 0.5(25 lp/mm) and the maximum relative distortion is 0.54% . The 3D construction method is effective and can tremendously raise the design efficiency of freeform optical system. And the freeform largefield imaging system designed with 3D construction method shows its advantage of much lower distortion and meets the balance between the high imaging quality and low distortion of the large- field imaging system, satisfying the future development requirement of remote sensing.

Based on the achromatic principle of composite wave plate and diffraction-limited theory of the tight focusing of the vectorial field, a pupil filter is presented for the focusing of the broadband vectorial field with the central wavelength of 600 nm. This filter is combined of three segmented wave plates, each of which is divided into four concentric belts with optimized radial parameters and azimuth angle. The optical axis of the two adjacent belts is vertical. For the incident vectorial beam with wavelength from 550 nm to 650 nm, the desired specially focused field with extended depth of focus, such as optical needle field with compressed radial width and diffraction-limited tube filed, can be achieved. The result shows that this filter can be effectively used as an effective manipulator for the vector beam with wide waveband in the 100 nm band. This achromatic pupil filer will be beneficial for the development of the focusing theory and applied technology about the wideband vectorial field.

Photonic crystal is an artificial microstructure constructed in optical wavelength scale, whose dielectric constant arrangement is a periodic configuration. Because it possesses photonic bandgap, it can be used to control photons. Photonic crystal waveguide can be formed by introducing line defect. Given 1.55 μm TE polarized light as source and under different waveguide separations, the relationship between coupling length, coupling efficiency and refractive index of dielectric cylinders, radius of dielectric cylinders are calculated and analyzed by finitedifference time-domain method, respectively. These research results will provide a theoretical guidance for the structure design and fabricating of the 1.55 μm coupler.

Targeting poor color rendering property of current white light-emitting diode (LED) lamps, based on the colorimetry method, the calculation model for color rendering index of synthetic white light is studied and the parameters like color temperature and color rendering index of the synthetic LED light source are obtained based on the spectrum and quantity of light sources involved in the synthesis process. By using optimized traversal range, the spectra of cold and warm white light and single- color LEDs are imported into the program for simulating calculation, obtaining the maximum value of color rendering index of the synthesized light source under different color temperatures as well as corresponding matched quantity of various LEDs. The results show that the synthesis with warm white LEDs and red, green and blue LEDs can lead to white light whose color temperature falls in the range of 3500 K~12300 K and color rendering index Ra ranges between 92.0 and 97.7. The synthesis with warm white LEDs and red, green and bluish-green LEDs can lead to low color temperature white light (3500 K~4500 K) whose color rendering index Ra ranges between 95.0 and 97.8. The synthesis with cold white LEDs and red, green and bluishgreen LEDs can lead to high color temperature white light (8200 K~13000 K) whose color rendering index Ra ranges between 90.9 and 98.4. An actual fabrication is conducted following the calculated LED amount to produce an LED module with 7803 K color temperature and 97.29 color rendering index. Actual measurement shows that the produced LED module has a color temperature of 7992 K and a color rendering index of 97.1, which is well matched the theoretical results.

Symmetric substructure dual gratings on the upper and bottom surface of the absorption layer are proposed to enhance the sunlight absorption for amorphous silicon thin-film solar cells. Using rigorous coupled wave method, it is found that in 600~750 nm wavelength range, the new gratings can effectively reduce the reflection from the upper surface of the incident light, the leakage transmittance from the bottom surface, and can enhance the absorption of amorphous silicon thin film solar cells with a thin absorption layer thickness of 400 nm. When the grating is adopted only at the upper surface, the optimized absorption can be increased by 71%; when it is adopted only at the bottom surface, the absorption can be increased by 24%; while for the case in which the gratings are adopted at both surfaces, the absorption can be enhanced by 81%. The study can provide new idea on designing high absorption and easily fabricated solar cells.

In order to understand the static birefringence and the circular dichroism of a photo-elastic modulator (PEM), an intensive study about the polarization characteristics of PEM is done. First of all, Muller matrices are used to describe the polarization characteristics of the photo-elastic modulation, the static birefringence and the circular dichroism. The general polarization modulation model of PEM is built. Then, the principle of the modulation model is studied, theory and simulation are analyzed. Finally, experimental apparatus is established and the polarization modulation experiment is carried out. The results show that the theory model built is reasonable and correct, the polarization modulation characteristic of PEM should be the combination of the small static birefringence,the photo-elastic modulation and the circular dichroism. Moreover, preliminary measurement for one example of PEMs shows that the circular dichroism is 2.755 × 10-2 , the phase retardation of static birefrigence is b = 5.73 × 10-2 rad and its direction angle is α = 3.96° . This study gives the general Mueller matrix form of a photo-elastic modulator, and expands the knowledge of the photo-elastic polarization modulation.

When the radial polarization vector beam is focused by a high numerical aperture lens, compared with the linear polarization light and the circular polarized light cases, a smaller focused spot can be obtained by the radial polarization vector beam. An elliptic annular aperture can enhance the axial component of light in the focus area. So the focus spot size can be further reduced in one direction. The focusing characteristics of the radial polarization vector beam passing through an elliptic annular aperture are studied. Two focusing lobes are obtained by the radial polarization component of light. An elliptical focusing spot is obtained by the axial component of light and the corresponding physical explanation is given. When the inner radius increases, the focus size of the focusing spot and focusing lobes can be less than one third of the wavelength in one direction. When the inner ring radius of the elliptic annular aperture is further improved, a smaller focus size of light can’t be obtained as the decrease of light and the diffraction effect. The results of the study are important for improving one direction resolution of laser scanning microscope.

The long-distance quantum key distribution network is difficult, since the secure transmission distance of traditional quantum key distribution (QKD) is not long enough. To overcome this problem, A measurement device independent (MDI) QKD protocol based on quantum memories(QM) and entangled photon sources(EPS) is proposed, as well as its network model. And indirectly heralding QM scheme and directly heralding QM with QM scheme based on EPS are compared. The relationships of the key generation rate, secure transmission distance, and hold time of quantum state about MDI-QKD protocol based on QM and EPS are also analyzed. The simulation results show that MDI-QKD based on QM and EPS compensate for the lack of MDI-QKD based on directly heralding QM, which is necessary for heralding QM, and the secure transmission distance is far higher than traditional MDIQKD and general MDI-QKD based on indirectly heralding QM. Furthermore, once the hold time of quantum state is greater than 1 ms, the key generation rate will be almost invariable. The double-channel and two-user network model are employed. The single-channel and multi-user QKD network can be implemented with time division multiplexer and fast optical switch.

How to directly measure the concurrence of two-qubit pure states without quantum state tomography is studied. A quantum circuit is designed which can encode the concurrence of a general two-qubit pure state into the probability of obtaining some specific states at the detection stage. Here, two copies of the initial state are needed in each measurement round and several operations, such as σz operation, simple qubit rotation R and parity-check measurement (PCM), are carried out on them. An optical implementation scheme for the direct measurement of the concurrence for polarization entangled pure state is proposed. Only one PCM for coupling two qubits is needed, which greatly reduces the complexity of the scheme. In addition, this scheme can directly measure the concurrence of remote entanglement.

In quantum Gaussian key distribution experiment, post-processing is one of key technologies to improve data reconciliation efficiency and guarantee the security of the extracted secret key. A specific data reconciliation of post-processing is proposed through the slice error correction which uses the quasi-cyclic low density parity check code and traditional low density parity check code to cascade to compress and code. To analyze the security of secret key extracted, direct reconciliation and reverse reconciliation scheme are proposed in individual attack and collective attack on the continuous variable quantum key distribution with homodyne detection. The result indicates that the data reconciliation efficiency can achieve 91.2% when code length is 2×105 and the third and fourth level code rate is 0.3/0.95. The amount of the extracted secret key can reach 3.98 kbit/s using the optimal attack and transmission distance can reach about 30 km, which proves the safety of the data reconciliation scheme and can satisfy the requirement of the metropolitan area network communication.

A kind of terahertz metamaterial with electromagnetically induced transparency (EIT) like resonance and its application in streptavidin-agarose (SA) specific sensing are demonstrated. Finite element method is used to analyze the high Q EIT-like resonance and its sensing performance. The label-free specific biosensor is composed of metamaterials functionalized by biotins and octadecanthiols for SA biorecognition experiments. The transmission properties are measured by a high-resolution backward-wave oscillator (BWO) spectral system. The results show that the EIT-like resonance of the metamaterial sensor has a high Q factor of 34 and a sensitivity of 24.7 GHz/RIU. Sensitivity of the resonance frequency shift to SA concentration is 0.65 GHz/(mg/mL). The results provide references for applying terahertz devices to label-free biological and chemical sensing.

The tunable diode laser absorption spectroscopy (TDLAS) technology and oxygen absorption lines near 760 nm are used to realize real-time on-line measurement of oxygen concentration. A detection system based on TDLAS direct absorption technique is designed. In order to solve signal amplitude fluctuation for on- site measurement, an automatic gain control module is designed using voltage controlled amplifier to achieve precise control of the spectrum signal amplitude; generalized Lorentz function is adopted to realize the approximate calculation of Voigt function combining Levenberg-Marquardt nonlinear fitting method to realize fast Voigt profile fitting of the absorbance spectrum curve, to meet the requirement of real-time on-line detection. Experimental results show that the algorithm can achieve Voigt profile fitting of absorbance curve. A fixed concentration of oxygen is continuously measured. Minimum detection limit of the system is 523 × 10-6 m, and standard deviation is 1.75%. Detection system is reliable and meets the real-time on-line oxygen concentration detection applications.

The Ebinur Lake Basin is selected as the studied area, and typical saline soil is chosen as the research object. By introducing fractional differential algorithm, setting 0.2 as the order interval and dividing 0~2 into 11 orders, the differentials of the raw spectral reflectance and its four mathematical transformations are calculated. Combining with the soil salt content measured in laboratory, the effect of fractional differential algorithm on soil hyperspectral data is explored from the perspective of correlation coefficient, standard deviation and information entropy, respectively. The results show that with the increase of the differential order, the number of bands whose correlation coefficient passes the 0.01 level of the significance test follows a decreasing trend and the 1 lg R transformation has better capacity to enhance the correlation coefficient than the other three mathematical transformations; the overall distribution of hyperspectral data becomes relatively concentrated and the difference among soil samples is gradually reduced; the total information entropy decreases, the disorder degree of the information becomes smaller and the amount of valid information increases. Fractional differential can detail the varying trend of correlation coefficient, standard deviation and information entropy, enrich the methods of hyperspectral data pre-processing, delve into spectral information based on the spectral dimension, provide a new perspective on the deep exploitation of hyperspectral data, and offer a reference for various applications of hyperspectral data, such as characteristic band selection and quantitative inversion of land surface parameters.

Due to the precision restriction of the system assembling and device location, the relative position of the two stepped micro-mirrors in spatial modulation Fourier transform spectrometer can appear the shift and rotation in the alignment process. Using the linear system theory and scalar diffraction theory, the model of the interferogram image and recovered spectrum corresponding to shift error and rotation error are established respectively. By means of the analysis to the calculation result, the marginal interferogram units are clipped by the shift error and rotation error, and the concomitant spectrum lines is appeared in recovered spectrum, bringing the spectrum noise badly. Finally, according to the action characteristics of the shift error and rotation error to interferogram image, a method of regional compensation to interferogram image is put forward, by extending the step number of two stepped micromirrors to expand the interference area, then using the internal effective interferogram units to recover the signal spectrum. Calculation shows that this method can restrain the influence of the alignment error effectively, and so as to decrease the location precision of the stepped micro-mirror consumedly.

Single- layer optical film prepared by electron beam evaporation possesses remarkable columnar structure. The variation of its internal film refractive index is large, so the induced volume scattering phenomenon is relatively obvious. Based on the first-order electromagnetic perturbation theory, the volume scattering theory model of single- layer optical film is established. The effects on volume scattering caused by layer thickness, polarization state of incident light, columnar structure factor and inhomogeneity are analyzed. For optical films with pure columnar structure, the variation law between the volume angle resolved scattering (ARS) of single-layer hafnium oxide (HfO2) thin films prepared by electron beam evaporation and the layer thickness is established. The ARS magnitude of volume scattering for pure columnar HfO2 films is similar to that of the completely uncorrelated surface scattering model. Within a certain range of film thickness, the ARS value of volume scattering increases with the increase of film thickness. For inhomogeneous thin films, the ARS value of volume scattering increases with the increase of film thickness when the inhomogeneity is constant. When the layer thickness is constant, the ARS value of volume scattering will decrease the increase of the absolute value of the inhomogeneity.

Aimed at the defect that spectral reflectance space is not a valid primary pigments linear mixing space, three principles of establishing the primary pigments linear mixing space are presented. The manuscripts are divided into three types, transparent pigment continuous tone, opaque pigment continuous tone and halftone (translucent pigment) according to the different optical properties of different original pigments. The linear spectral spaces of real physical domain that can reflect original pigments really for these manuscripts respectively are built up. Experimental verification is carried out taking opaque pigment manuscript as an example. Experimental results show that the pigments mixing linear space according to optical properties of original pigments is a valid linear mixing space, of which the spectral can correctly estimate the numbers of primary pigments and approximate the spectral shape of each primary pigment.

Grating-based X-ray differential phase contrast imaging has great advantages of detecting the low- Z materials compared with conventional X- ray absorption imaging. It has potential applications in the field of materials, security and medical diagnostics. The fabrication process of absorption grating which is a critical optical component in the system is difficult and costly, and the absorption grating cannot completely absorb high- energy X- rays that results in the decrease of image contrast and detection sensitivity, which has been a great obstacle for the practical application. In view of above problems, a low cost and high efficiency approach based on Bi-source grating and structured scintillator is proposed. The scintillator overcomes the limitation of high- energy X- rays and proposes the function of analyzer grating. This approach obtains high quality phase contrast image experimentally.