The vertical Rayleigh-Sommerfeld (VRS) diffraction theory is used for analyzing and calculating the focused field distributions of high-numerical-aperture (NA) multi-step hybrid Fresnel zone plates (M-SHFZP). Under the illumination of linearly-polarized light, results are shown as follows: 1) Due to the transmission coefficient of the film changing with the depth of steps, the focused intensity of M-SHFZP is smaller than that of multi-step pure-phase Fresnel zone plates (M-SPFZP). However, the focal spot size of M-SHFZP is almost the same as that of M-SPFZP; 2) As the step number increases, the focused intensity increases, but the spot size is invariant; 3) The diffraction field presents a multispot distribution for low-NA M-SHFZP, but the intensity of high-order foci is effectively suppressed for high-NA M-SHFZP. The more the step number and the higher the NA, the stronger the ability of M-SPFZP to suppress higher-order foci. The results obtained by the VRS agree with the results obtained from the finite-different time-domain (FDTD) simulation basically.

A novel polarizer based on high birefringence photonic crystal fiber (PCF) is proposed. Through using cladding defect structure and resonance coupling, a single- polarization mode and 23~250 dB extinction ratio in the wavelength range of 1250~1850 nm has been achieved.

In all-optical quartz-enhanced photoacoustic spectroscopy (QEPAS) system, a Fabry-Perot demodulation method based on operating point stabilization technology is proposed. For improving the detection accuracy of the photoacoustic signal, a tunable erbium-doped fiber ring laser is used as the detection light source and a detection technique based on the direct-current error signal is employed to lock the operating point to the quadrature phase point in the system. The experiment for detection of water vapour in the open environment is carried out and a normalized noise equivalent absorption coefficient of 1.81×10-7 W/(cm· Hz ) is achieved, which is about 1.2 times higher than that of conventional QEPAS.

A kind of relative humidity sensor based on March-Zehnder (MZ) interference is proposed in this paper. The sensor is composed by splicing with a waist enlarged single mode fiber (SMF) with a length of 15 mm between two SMFs, whose surface is coated with a thin layer of 5% polyvinyl alcohol (PVA). With the humidity changing, and the effective index of the cladding mode changes. When the relative humidity changs, the central wavelength of the interference peak shifts, so that the relative humidity can be obtained by measuring the sensor′s transmission spectrum. The sensitivity of the proposed humidity sensor is 0.0983 nm/% RH measured by experiment. Experiments also show that the MZ-based humidity sensor has a good stability and a series of other outstanding advantages.

Based on the Jones matrix, the optical transmission model of dual depolarized fiber optical gyros (DFOGs) is built and the theoretical expression of polarization crosstalk error is derived. The effect of the polarization crosstalk error caused by the 45° angle error of depolarizer, the power coupling of polarization crosstalk point, the limited Y waveguide chip extinction ratio and the angle of polarization rotation of the fiber coil on DFOG are simulated and analyzed. Experiments demonstrate the effect of 45° angle relative error between two depolarizers and temperature on DFOG zero drift. Results show that the greater the 45° angle relative error between two depolarizers changes and the higher temperature gradient is, the greater influence on the precision of DFOG will become.

In view of the Fiber Bragg Grating (FBG) sensor network monitoring the static loading on the aircraft wing box test piece, self-repairability of the FBG structural health monitoring system based on multi-agent technology is studied. When partial sensors signal can′t be acquired in certain agent, firstly, the support vector regression algorithm is used to predict the external loading damage position with the acquired sensor signals in each agent, and then the cooperative agent is used to cooperate each agent predicting result, so as to compensate the invalid sensor signals, thus the final predicting results are obtained for the structural health monitoring system. The research results indicate that the average predicting accuracy of the external loading position by the multi-agent technique is higher than that of any one agent, the invalid sensor signals can be compensated to some extent by the multi-agent technology.

In order to reduce the sensitivity of the polarization beat length with wavelength and expand the operating bandwidth of the polarization device made by the holey fiber, the holey fiber with diamond lattice, the influence of the special holes near the core, the bottom holes and the pitch of diagonal holes on the wavelength sensitivity of polarization beat length are analyzed. The preliminary optimal cladding structure parameters are obtained. The polarization beat length remains stable in a wide wavelength range. The results show that the relative variation of polarization beat length is less than ± 4% in wavelength range of 1.2~1.7 mm and the operating bandwidth can reach 500 nm while the error tolerance of optimized geometric parameters is greater than 0.1 mm. The more feasible process structure parameters are provided for drawing the achromatic holey fiber wave plates with broadband.

With the characteristic of flexibility, unmanned aerial vehicles (UAV) can adapt to the flight mission of complex terrain in cloudy area. But because the lens are short and the obtained image with the characteristics of small size, large number, short baseline and irregular overlapping degree, this method is different from the one processing traditional aviation image. In order to solve the precision of block adjustment which is not high and the heavy workload of image processing based on UAV image. We took several methods, first of all, the image data acquired by UAV are processed using the conventional block adjustment method, and then the POSsupported block adjustment method is used based on the original POS data. For the problem of low accuracy of the original POS data obtained by UAV, POS data correction model is established and POS data error correction parameter are acquired by layout a small amount of the control points in regional network, and a POSsupported block adjustment method is proposed based on the corrected POS data. Experimental results show that the precision of the conventional method is superior to the method of using original POS data directly, the precision of the corrected POS data method is close to the conventional method, at the same time, the efficiency of the block adjustment is improved.

High precision refractivity of optical glass is an important condition to ensure the image quality, mainly by the V- prism refractometer detection. In V- prism refractometer in using image alignment, the image quality of single line in the collimator directly affects the alignment accuracy in measurement, especially as the contrast between single line and background is low, affects the accuracy in measurement. A combination of selfadaptive gray equilibrium and vertical projection is proposed. This method can extract the low contrast single line, prove the effectiveness of the algorithm through the comparative experiments, and improve the angle measurement accuracy to ± 1″, repeatability superior to 1 × 10- 6, and algorithm stability is good. It has important practical significance to achieve high precision measurement of optical glass refractive index.

The operating distance is one of the most important comprehensive performance indexes. Based on the imaging principle of this AlGaN solar-blind UV focal plane array (FPA) imaging system considering the influence factors of the UV system, the distance of point target and extended target are calcnlated respectively. The influencing factors of the solar-blind UV imaging system include the feature of target, the attenuation of the atmosphere transmission, optical system and UV FPA detectors. From the transfer of radiation energy of targets， the operating range theoretical formulas are deduced combing the relationship of signal-to-noise, fault prediction and detection prediction. Finally, the system parameters are inputted into the operating formula. The operating formula can provide theoretical basis for performance assessment of the UV imaging system. The operating rang can be improved by the means of increasing effective optical aperture, optical transmissivity, integration time and adopting noise reduction methods.

Optical transmissivity parameter is an important parameter in evaluating the optic aiming device′s imaging luminance and clarity. This paper introduces an optical transmissivity detection system with a wide spectrum coverage and high precision for the aiming device, which is mainly applied to the production and test process of the aiming device. Focused on influencing factors on the measurement accuracy in the detecting process including polarization, beam displacement, stray light, spatial uniformity and nonlinearity of detector, quantitative analyses by verification tests or tracepro simulations and combinded standard uncertainty of highaccuracy measurement for spectral transmissivity are presented. According to the nonlinear error of detector, a correction is carried out by using the principle of least square method. The results of the calibration experiment have proved that the accuracy of transmissivity parameter in visible and infrared bands arrive at 0.35% and 0.65%, respectively.

Since the focal length of the lens based on traditional measurement has large error, the Quasi-Monte Carlo algorithm is adopted for analysis. The liquid crystal display screen differentiation graphics are used instead of parallel Perot plate light pipe. Then least square fitting is used to calculate the focal length. Adaptive Quasi-Monte Carlo algorithm sampler is adopted for imaging sampling, and according to the brightness difference of each pixel and its neighboring pixels, different number of samples are produced. The sampler has no limit control values, so the Hardy-Krause is used to decide the bounded variation function. By Dovi Lebegue method, the error of the Quasi-Monte Carlo method is decided by the star deviation error of random sequence. Simulation shows that the standard deviation of the focal length measured by LCD screen is smaller than that measured by visual measuring, and that root-mean square error of Quasi-Monte Carlo algorithm is smaller than that of the Monte Carlo algorithm.

The pure phase type of spatial light modulator (SLM) is a widely used high precision optical device. The double-hole interference method recommended by Holoeye can correct the phase to a result which has 80% of 1st diffractive efficiency for 16 level blazed grating. But the total process needs to be conducted carefully with filtering collimation, beam expanding etc., and it takes too long time. The diffractive method using binary grating can simplify the correction process. We make a measurement just every 10 gray level. The total 256 values are achieved by interpolation using Matlab. As a result, the 1st diffractive efficiency of 16 level blazed grating and binary grating reaches to the Holoeye catalog values of 83% and 40% respectively. The experiments prove that the diffractive method based on the stable averaged phase modulation of Holoeye Pluto SLM can correct the characteristic of SLM with simplicity and feasibility, and it is not limited by the phase flicker under 5-5 sequence configuration of SLM.

The dispersion of optical material influences the accuracy of lens gap measurement. In order to improve the accuracy of lens gap measurement, the effect of optical material dispersion is investigated by the theoretical analysis and numerical simulations. An expression of interference signal offset is obtained by numerical simulation for materials of LAK, ZF6, H- ZF2, BAK7 and K9，with the offset proportional to the first order dispersion coefficient of optical material. An experimental platform is set up to verify the simulation result, and it is shown that the relative error of interference signal offset between the experimental and simulation results is below 2% . Considering various error factors in the experiment, the relative error of 2% is reasonable and the obtained expression via simulations is correct.

In linear structured light measurement, in order to extract the point cloud normal vector quickly and accurately. A circumcircle extraction method is presented. Every three consecutive points are collinear or not is determined after the initial light stripe centers have been obtained by refining method. If they are collinear, the normal slope can be calculated by the points. Else, the three points determine a circle. The normal can be gotten by connecting the circle center and the initial center point. In order to reduce the shock, the average value of each three normals are calculated as the last normal. Experimental results show that the presented method can accurately extract the normal in comparison with Hessian matrix method and Sobel gradient method, and the time to process a 320 pixel × 240 pixel image is less than 8 ms, which can meet the real-time requirements.

A photoelectrical test method and the system are developed for messuring the optical performances of some scintillation crystals. The theoretical critical focal length of the measurement system is deduced and used in order to make the most of both X-ray photons and the effective area of the scintillation crystal panel. Furthermore, coaxial cable ordered is used to replace the carried wire to remove power noise. Experiments are successfully done to integrally test the spectral response, conversion efficiency and spatial resolution of some scintillators made by Shanxi Changcheng Microlight Equipment Co. Ltd. and the results show that the presented system is helpful to test the scintillator properties.

White light interferometry is employed to research on the measurement technology for large scale evaluation and a dedicated system is developed on the platform of nano-measuring maching (NMM). Firstly, this work calibrates the environment effects and the results are given quantitatively. Secondly, under the condition of the precise environment control, the non- overlapping stitching method is investigated, and the comparison of the results is also made; For non- periodic array aspheric optical surface, white light tilted scanning interferometry is employed to perform the large range measurement. During the scan, the specimen moves through the coherence area along a sloping direction, and the objective field of view limitation is removed. ence, within one round of scan, the surface in millimetre scale can be successfully evaluated. For the scanning process, this article analyzes the interferogram slipping out and the impact due to the difference of the two angles appeared in this technology. Finally, the comparison between the above two methods is given.

Balling phenomena is a common defect in selective laser melting (SLM) process, it is the main reason causing high surface roughness、pores、tilt delamination and other defects, seriously affect the density and mechanical properties of parts. The classification and formation process of balls、influencing factors and hazards of balling phenomena at home and abroad are summarized systematacially. Results show that different metal balls have different formation mechanisms. The formation process of balling phenomena is complex, and many factors during fabricating affect the formation of ball reaction. But the current researches at home and abroad of balling phenomena are not systematic, comprehensive and thorough enough. It will be useful for restraining and eliminating balling phenomena during SLM process to research on the influence of technological parameters, physical and chemical features of powders on balling.

A picosecond pulse laser with central wavelength of 1060 nm and adjustable output waveform is used as the seed source. This seed source is amplified by an Yb-doped double cladding fiber amplifier, and the output pulse width can be adjusted between 0.5~10 ns. In each waveform of the master oscillator power amplifier (MOPA) fiber laser, the highest average power is in the range of 18~21 W, peak power is in the range of 11~13 kW, and single pulse energy is in the range of 0.02~0.13 mJ with a near single-mode beam (M2=1.5). This high peak power, high single pulse energy and high average power fiber laser can meet the requirements of the area of the laser machining, material processing and the nonlinear transfer, and is a significant light source for some material which is sensitive to the heat when processed by lasers.

In order to expand the applied range of diode laser in laser processing field, and to apply diode laser to the thick plate welding of metal materials, the fiber coupled diode laser of LDF4000-40 that developed by the Laserline company is adopted to investigate the welding performance of the thick SUS304 austenitic stainless steel. Experimental results show that the keyhole can be formed, proving the ability of strong penetration. Compared to the fiber laser welding under the same welding conditions, the weld penetration depth decreases and bead width increases slightly; weld forming and welding process stability is better, and spatter is significantly smaller. The results confirm that the fiber coupled diode laser can be used for the thick plate welding of metal materials.

3~5 μm mid-infrared lasers have attracted much attentions due to their wide applications in defences, medicine, free-space optical communication and materials processing. A new scheme for obtaining a 3~5 μm flexible-wavelength, compact mid-infrared Raman fiber laser is proposed, using a 2.7~2.9 μm Erdoped fiber laser as Raman pump source and a ZBLAN fluoride fiber as Raman gain medium. Based on the nonlinear coupling equations of Raman fiber lasers, the 3~5 μm mid-infrared ZBLAN fiber 1st/2nd-order Raman lasers are numerically analyzed and optimized. The theoretical optimization is mainly focused on the effects of ZBLAN fiber length and output-mirror reflectivity on the Raman laser threshold and output power. The numerical results show: 1) the Raman laser threshold significantly reduces with the increase of the outputmirror reflectivity, and there always exists the optimized ZBLAN fiber length for the lowest Raman threshold (4.15 W); 2) in order to obtain the high-power Raman laser output, the optimized reflectivities of output mirror are 84~98% (1st-order) and 42~60% (2nd-order), the optimized ZBLAN fiber lengths are 6.7~8.9 m(1st-order) and 1.5~2.4 m (2nd-order), respectively. The optimized slope conversion efficiencies can be as high as 72.36% (1st-order) and 34.06% (2nd-order). These results could provide a theoretical guidance for such mid-infrared fiber Raman lasers.

High-order Hermite-Gauss modes are transformed from fundamental Gauss mode using mode converter cavity by mode-mismatching technique between input beam and cavity. Based on the nondegeneration of resonant cavity lengths and output amplitudes of different order Hermite-Gauss modes, an auto-searching and auto-locking servo system of cavity for high-order mode generation is realized and stable Hermite-Gauss modes of TEM00, TEM10 and TEM20 are obtained experimentally.

Theoretically analyzes the Raman crosstalk cancellation under the wavelength conversion technologies which used in central transmission in the dense wavelength division multiplexing system. The regularity of outputpower and amplifier is given, and the simulations has important significances in further study.

Acousto-optic tunable filter (AOTF) is a new type of dispersion components. It is widely used in the field of hyper-spectral imaging, but diffraction angle changes along with wavelength when tuning, which will cause drift of images. To solve the problem caused by crystal dispersion of AOTF spectral camera, a prism is added to the emergent surface of the crystal. Through the analysis of crystal optical rotation influence on crystal outside diffraction angle, it is found that when the incident angle is very large, crystal optical rotation must be taken into consideration. According to the basic analysis above, the relationship among prism vertex angle, the prism material and prism deviation angle is analyzed. The results show that when the incident angle is 28°, dispersion residual deviation of 0.0007° is achieved by adding 10.1° prism. This implies that the dispersion of AOTF spectral camera can be eliminated by adding the prism of proper material and vertex angle.

A super-resolution focusing and easy integrated sub-wavelength metal single-slits containing mental strip structure is proposed based on sub-wavelength metal slit focusing structure. The focusing properties of the structure are simulated and analyzed by using electromagnetic field simulation software finite difference time domain (FDTD). Through the analysis of structural parameters of focusing structure influence on the focusing effect, a high focusing intensity of I=4.5 and a small spot size with full width half maximum (FWHM) of 300 nm (lass than λ /2, λ =632.8 nm) is achieved. Meanwhile, the structure′s deviation and positioning accuracy of ±10 nm have little effect on the focusing property. Such a focusing structure with the predicted focusing efficiency has potential practical applications in nanophotonics and integrated photonics due to the small lateral dimension size of only about 2.0 μm.

A novel wavelength-division demultiplexer based on equilateral three-core optical fiber is proposed. Compared to the wavelength-division demultiplexer based on photonic crystal fiber, it has the advantage of being easier to make and to link with conventional optical fiber. Two parallel mismatched cores are designed to be phase-matched (or index-matched) at certain wavelength. Then the light in the two cores will be fully coupled, which will lead to filtering. By selecting a suitable fiber length, different wavelengths of the input light can be output at different cores end of the optical fiber to achieve the function of wavelength-division demultiplexer. Numerical simulation by beam propagation method demonstrates that a 10.25 mm long wavelength-division demultiplexer based on equilateral triangle arrangement three-core optical fiber can separate 1.31 μm wavelength light from 1.55 μm wavelength light.<网络出版日期?2014-05-16

Effects of the parameters of each layer on the performance of back-illuminated separate absorption and multiplication hetero-junction AlGaN avalanche photodiodes (APDs) with the polarization effect are investigated numerically, and the detailed physical mechanisms are explained. The results show that the breakdown voltage for the APDs can lower significantly and the gain increases pronouncedly with the optimization of these parameters. The maximum gain for AlGaN APDs with p-GaN layer has been improved more than 300%. This is because the polarization induced charge at the GaN/Al0.4Ga0.6N hetero-interface controls the distribution of the electric field of multiplication, inserting and absorption layer, and enhances the efficiency of injection and multiplication of carriers. Meanwhile, the optimization of the parameters can decrease the dark current of APDs at breakdown voltage.

With the increasing demand for the communication capacity, the optical frequency combs based on micro-ring resonator can satisfy the requirements of communication systems. The optical frequency comb has the features of wide spectrum, high coherence and integration. The optical frequency comb generation is based on the four-wave-mixing(FWM) effect in micro-ring resonator, so the requirement of dispersion curve about resonator is more stringent. This paper summarizes several latest researches about dispersion control of microring resonator, including change the micro-ring width, the combination of slot structure and micro-ring structure, the use of photonic crystal structures. Up on these, we can make a comparative analysis of their strengths, weaknesses and performance. Also there is a prospect on the further optimization of micro-cavity dispersion curves. Utilizing the combination of micro-ring and photonic crystal structure, may realize an optimization of dispersion curves in small spectrum, and improve the efficiency of FWM.

Physical random numbers have great application value in the fields of cryptography, communication and national security. Conventional physical random number generators are limited by the low bandwidth of applied entropy sources such as thermal noise and thus have low bit rates at Mb/s order. With the appearance of wideband photonic entropy sources (e.g. chaotic laser and amplified spontaneous noise) in recent years, lots of schemes for high- speed random number generation are proposed. Among them, chaotic laser attracted many attentions due to its merits such as high bandwidth, large amplitude fluctuation and ease of integration. According to the international research situation, physical random number generation schemes based on chaotic laser are overviewed. Through analyzing their own advantages and disadvantages, current hot spots in the studies are summarized and some possible development orientations in the future are pointed out.

Single-layer, double-layer and multi-layer coating lycopene nanocapsules are prepared by the micro-emulsion technology and composite reunion method, and the effect of coating materials on particle size and its distribution is analyzed by dynamic light scattering method. The studied results show that the more serious aggregation can be produced in phosphate buffer of pH=6.5 for the single-layer lycopene nanocapsules coated by alkali-treated gelatin. Compared with the single-layer coating lycopene nanocapsules, the weaker aggregation can be observed in phosphate buffer of pH=5.5 for the double-layer lycopene nanocapsules coated by alkali-treated gelatin and k-carrageenan. However, the multi-layer coating lycopene nanocapsules can be dispersed in stability in phosphate buffer of pH=5.5 and there is no aggregation.

Different test methods are used for analyzing Burmese deep lavender color jadeite sample before and after heat treatment. Phase analysis shows that this kind of jadeite is assigned to jadeite jade. X-ray fluorescence spectrometry indicates that the deep lavender color area has more amount of Mn and Fe than the white one. Electron paramagnetic resonance spectra demonstrates that Mn mainly exists in the form of Mn3+ rather than Mn2 + in traditional opinions. Ultraviolet-visible absorption spectrum reveals that wide absorption band centered at 572 nm can be attributed Fe2 + ion couple-electron pair 5A1(5T2) →3T1(3H) transition and the charge migration of Fe2 +-Fe3 + ion pair,which are the main reasons for deep lavender jadeite coloring. The superposition of 6A1(S) →4T2(G) and 6A1(S) →4T1(G) d-d electron transition at 545 nm of Mn3 + ion can be considered as another factor of lavender jadeite coloring.

VOx thin films are deposited on K9 polished glass substrate by RF magnetron sputtering at various oxygen partial pressures. The surface profiler is used to measure the thickness and deposition rate, and the X ray diffraction is employed to detect the crystalline structure of the films. Surface morphology of the films is observed by afomic force microscopy (AFM). Transmittance spectra of the films are measured by the spectroscopy in the range from ultraviolet to near infrared. It is indicated that the VOx thin films take on crystalline state with different phases, and adjusting oxygen partial pressures can get optical films with weak absorption from visible to near infrared region, but high oxygen partial pressures go against with deposition rate of the films. Oxygen partial pressures have the influence of different degrees on the surface roughness and crystal growth pattern of the films.