A sectional magneto-optic fiber Bragg grating (MFBG) is the grating structure fabricated by writing multi-subsectional gratings onto a magneto-optic fiber. According to the coupled-mode theory for uniform MFBGs and the boundary continuity conditions of the electromagnetic field,the spectral characteristics of the circularly polarized light in the multi- sectional MFBG were theoretically studied. The research indicates that,the optical spectrum of the one-sectional MFBG is identical with that of the uniform MFBG,and the theoretical results of polarization dependent loss are consistent with the experimental data. The analysis also shows that sectional MFBGs are useful for photonic information processing such as adjustable comb filtering,optical clock extraction and tunable dispersion compensation.

A new method of dynamic target distance measurement based on self-mixing speckle in an erbium-doped fiber-optic ring laser is studied. The model of self-mixing speckle measurement system is presented,and the theoretical analysis of the production of self-mixing speckle signal is also given. Through the experiments,the dynamic speckle signal is obtained. The spectrum energy density analysis is applied to the dynamic speckle signals,and a linear relationship between the spectrum energy density and the detection distance is obtained. The result shows that highly precise distance dynamic measurements can be performed by using self-mixing speckle and fiber laser.

An adaptive optics (AO) retinal imaging system based on liquid crystal spatial light modulator was presented,which was operated on open-loop and two-wavelength mode.The system adopted a Shark-Hartmann wavefront sensor (SHWS) and a liquid crystal spatial light modulator to detect and correct wavefront aberrations respectively.830 nm near infrared light was used for the wavefront detection,and 790 nm near infrared light was used for retinal imaging.The open-loop mode can enhance the light efficiency and improve the system stabilization;the two-wavelength mode can enlarge the view field.The subsystems of pupil monitoring and respond matrix measuring were introduced to make the system more convenient.Some key parameters were introduced,and the optical system was simulated and analyzed with ZEMAX.It shows that the optical system can reach the diffraction limitation,and MTF@50 lp/mm of 0.25 (3 μm at retina),which satisfies the design requirements.

Median filtering is a spatial-order-statistics based image denoising method,which can preserve image details well while eliminating noise. In traditional median filters,the pixels in a square window is often sorted by bubble sorting,which demands large comparison times and long processing time,and is unfit for real-time image processing. Based on image parallel processing technology,a fast median filtering algorithm based on extended window is presented. In the proposed algorithm,the traditional square window is extended transversely,so the sliding step of window roaming can be increased by pixels to achieve much higher processing speed for the whole image,while the comparison results within the process of executing the algorithm are effectively used. The result shows that the algorithm can achieve high precision and real-time ability in image denoising. The algorithm improves the image processing speed by the cost of more area of hardware chip,and it is suitable for implementation on hardware such as field programmable gate array.

The theory of submerged objects detection based on Brillouin scattering is introduced,and the relative experiment on the foundation of new ICCD camera system is done. The results indicate that the submerged objects detection technology based on Brillouin scattering has great advantages in detection depths and can detect invisible objects.

The inclusion of freeform elements in an optical system provides opportunities for numerous improvements in performance.However,designers are reluctant to utilize freeform surfaces due to the complexity and uncertainty of their fabrication.Single diamond turning is a novel machining process capable of generating freeform optical surfaces or rotationally non-symmetric surfaces at high levels of accuracy.In order to achieve good results with this technology some key parameters need to be satisfied.These parameters include tool geometry,tool path generation,tool radius correction,and servo system performance.The servo capacity of slow-tool-servo machine is analysed,and a method to determine tool geometry parameter based on surface analysis is developed.The methods of tool radius compensation and tool path generation to ensure the stability of X-axis are researched.Experiment results show that slow-tool-servo machining technology can be used in preparation of optical free form surfaces element.

The effect of die design on coating concentricity of optical fiber at high drawing speed is investigated. In high speed drawing process,the pressure gradient of coating in die determines the magnitude of centering force and the concentricity of coating layers. The results of calculation prove that the flow of coating in conical shaped die can create pressure gradient of coating in die. The shape and size of die have very important effect on the magnitude of pressure gradient. The increase on taper and length of die will increase the pressure gradient,while the increase on diameter of hole can reduce the pressure gradient. Based on the optimization of die design,the average deviations of concentricity of primary and secondary coating layers of fiber drawing at 1800 m/min can be reduced to 1 μm and 2 μm respectively.

An improved Gerchberg-Saxton (GS) algorithm for constructing fully continuous phase plate for beam shaping is proposed. The continuity of the phase plate can be ensured by use of phase unwrapping algorithm and Fourier filter operation,and a better far-field intensity profile can be obtained when the objective amplitude is replaced with a proper modified amplitude function during iteration. The simulation test proves that the method has resolved the conflict between the demand of the phase continuity in the phase plate designing and the optimization of the target beam intensity profile. The demand of the distribution continuity for beam smoothing element,good profile of the target beam and high energy centrality in inertial confinement fusion can be satisfied simultaneously by this algorithm.

A review on the research status and advances of sensors used in the trace explosives detection is presented. Various trace detection technologies such as optical wave spectroscopy,gas chromatographic technique,Ion mobility spectrometry,surface acoustic wave,MEMS,mass spectrometry,fluorescence and biosensor are introduced. Working principles and detection performance of different sensors are analyzed.

Post-processing techniques of photonic crystal fibers (PCFs) are discussed and analyzed in detail,including taper,taper after inflation,controlled hole collapse. Using these techniques,the configuration parameters of the PCFs can be easily changed,such as hole size,core diameter,core shape and so on. Many types of PCFs devices can be made by using these techniques.

The basic principle of image processing methods based on partial differential equations (PDE) is introduced,the variational methods used to derive PDE models are described,and the energy functional of widely used PDE denoising models is given. Our recent works of PDE-based image processing on electronic speckle pattern interferometry (ESPI) are reviewed,including performing contrast enhancement and denoising simultaneously for ESPI fringes,proposing new oriented PDE denoising models for dense ESPI fringes and a nearly preprocessing-free method for skeletonization of gray scale ESPI fringes. The main advantages of our methods are given and some suggestions are presented for the development and the research of PDE-based image processing methods on optics test technology.

A review of cavity ring-down (CRD) techniques,including pulsed-CRD,phase-shift CRD,narrow-band continuous-wave CRD,and optical feedback CRD,for accurate high reflectivity measurements is presented. Corresponding principles,advantages and disadvantages are described in detail.

Coherent beam combining of fiber lasers can achieve high power laser with good beam quality. Most studies on coherent beam combining focus on phase controlling,i.e.,how to make the beamlets coherent. Beam combining of the coherent beamlets,i.e.,how to improve the fill factor of the coherent laser array,is also an important factor that affects the beam quality,yet it has seldom been taken into account. In order to ensure the beam quality of the coherently combined beam,the aperture filling technique should be employed to improve the fill factor of the fiber laser array. Recent progress on the aperture filling technique,i.e.,amplitude-to-phase technique,self imaging waveguide,beam shaping,diffraction optics and beam truncation was introduced. Each technique was analyzed and evaluated in detail. It is shown that the beam truncation technique is free of complicated optical system design and easy to implement,which holds great potential in coherent beam combining of high power fiber laser array.

Deformable mirror (DM) is a very important element in adaptive optical system,and it can perform dynamic phase modulation and endow optical system the ability to decrease the influence of dynamic wavefront errors. Deformable mirror of conventional adaptive optics can not satisfy the need of miniaturization and integration,but the deformable micro-mirror based on microelectro-mechanical systems (MEMS) can solve these problems. The theory and development of MEMS-DM and its application in adaptive optics are summarized,the fitting capability of MEMS-DM are discussed. At last,a prospect of MEMS-DM is given.

The developments of Terahertz (THz) spectroscopy and imaging technology in recent years are reviewed,including THz time-domain spectroscopy,time-resolved THz spectroscopy,THz emission spectroscopy,time-domain raster scan imaging,real-time imaging,tomographic imaging,continuous-wave imaging,and near-field imaging. Fundamental principles involved in THz spectroscopy and imaging techniques are introduced. Potential applications of THz technology,such as homeland security,biological research,materials research,non-destructive evaluation are discussed.