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In this paper, we propose a high-density grating interferometry system, which can be applied to measure displacement on the nanometer precision. We make use of the optical subdivision module to improve the measurement resolution which is better than the traditional one. The core part of the whole system is a grating with high-density of 1780 lines/mm and long-range of 100mm*100mm. The apparatus adopts a symmetrical structure to reduce the error resulting from environmental disturbance. The system provides a novel measurement technique to improve the grating interferometry. The experimental results show that the grating interferometer system has good stability, and the in-situ measurement error is within +/- 5 nm for a long time. The grating interferometer can measure the short distance displacement of 30 nm and can control the error within +/- 2 nm. The measurement of the distance of 10 mm can control the error within +/- 20 nm. The results proves the feasibility of our proposed improved.

从理论上和实验上对飞秒激光脉冲通过散射表面后的时域特性进行了研究分析.用频率分辨光学开关法对通过散射表面前后的飞秒脉冲进行了测晕和对比.理论分析和实验结果表明,由于散射表面对飞秒脉冲的散射导致飞秒脉冲的展宽和形状的畸变.输入脉冲在时间相关函数的半峰令宽为64 fs;透射脉冲在时间相关函数半峰全宽的平均值为117 fs.对透射脉冲场的统计特性进行了讨论,逶射脉冲场实部和虚部的概率甬数分布遵从高斯函数分布;强度的概率分布遵从指数分布规律;给出了入射飞秒脉冲强度的自相关函数分布和飞秒时域散斑场强度的互相关函数分布的实验结果,并且对二者的时间相关函数进行了讨论.

An optically fixed photorefractive correlator is presented, where two-centre non-volatile holographic recording is employed to write and fix the matched filter in doubly doped LiNbO3 crystals. This correlator shows good correlation characteristics and insensitivity to the writing beam during readout. It can be used in cases requiring stability and not requiring modification for a long period and it is refreshed optically when new information needs to be registered.

A Dammann grating coupling method and corresponding coupling condition are proposed. The different diffractive efficiency of the traditional 3x3 Dammann grating are analyzed by using both the scalar diffraction theory and the Fourier Modal Method (FMM). One new 3x3 Dammann grating is designed by using FMM in association with the simulated annealing optimization (SAO), and its diffraction efficiency and uniformity are about 40% and 15%, respectively. The new 3x3 grating and one traditional 64x64 Dammann grating are then coupled and analyzed numerically. The diffractive efficiency and the uniformity of the final 192x192 dense spots array are 30% and 18%, respectively. As the reference object, one 121x121 beam-splitting grating is designed, whose uniformity and overall diffractive efficiency are 50% and 85%, respectively. Numerical results show that the Dammann grating coupling method is more economical and applicable way to generate dense spots array.

Dammann grating is useful in information technology as an optical splitter. It is usually fabricated through complicated processes. Here we report on the direct fabrication of a 6×6 Dammann grating in a silica glass by an 800 nm femtosecond laser. We also discuss the relationship between diffraction efficiency of 1×2 Dammann grating and laser irradiation conditions.

We propose and experimentally investigate a new scheme capable of suppressing light-induced scattering by periodical incoherent erasure during every non-volatile holographic recording cycle in photochromic LiNbO3:Fe:Mn crystals. The results demonstrate that the scattering noise is suppressed effectively, and the final diffraction efficiency of the fixed grating is significantly enhanced, rather than decreased, by about 30% compared with the conventional recording procedure. The period of the recording and incoherent erasure cycle is theoretically calculated and experimentally optimized.

The Kukhtarev two-center model for photochromic doubly doped LiNbO3:Fe:Mn crystals is both numerically and analytically solved for the recording sensitivity and the fixed nonvolatile space-charge field. An optimal prescription for material doping and oxidation/reduction processing is found, which requires that the crystal should be strongly oxidized together with a suitable Mn density with respect to the Fe density. Experiments performed with an oxidized crystal and a reduced crystal prove the prediction.

The effect of annular binary phase filters (BPF) on red-light high density optical disk system is investigated. Experimental results show that optical pickups with the BPF of 130 nm etching depth can successfully read out 15G byte disks.

In a traditional sense, Dammann grating can transfer the beam into one dimensional spots or two dimensional spots,which can be used for beam splitter or array illuminators. This paper presents a new kind Dammann grating that canrealize the equal peak value intensity circular diffractive field. We call it circular Dammann grating. And the order ofthe grating is the number of the circular diffractive spectrums. We use the binary phase-only mask in our numericalsimulation, we have obtained the optimized parameters, including the circular phase and radius of each ring. Ouroptimization algorithm is the simulated annealling algorithm. Different order circular Dammann grating can generatedifferent circular diffractive field. We have calculated the number from 1 to 9 diffractive spectrums and found that withthe increase of the encoding number of circular Danimann grating, more circular equal-intensity diffractive spectrumscan be realized. Different order Dammann gratings have practical applications for different purposes. For example, thefirst order circular Dammann grating produce the smooth intensity in the central lobe, which can be used as the flat-topintensity for the wide applications of optical interference, such as producing optical fiber grating, optical detection, etc.The multi order Dammann grating can be used for beaming shaping and laser demonstration. In conclusion, circularDammann grating is a novel diffractive optical element that has wide applications in optical information system.Keywords: Diffractive optics, Dammann grating, pure-phase plate, nanometer technology.

A novel device for generating femtosecond double pulses is constructed, which mainly consists of three Dammann reflection gratings. Being free from transmission elements, pulse distortion is avoided. Measuring the generated double pulses with a home-made second-harmonic generation frequency-resolved optical gating, experimental results demonstrated that this device can generate double pulses exactly equal in pulse intensity and pulse width with arbitrary delay time. This method should be highly interesting for double pulses generation and its practical applications.

A well known optics phenomenon finds new applications in emerging fields, including optical computing and optical measurement.

When linearly polarized light is focused using a high numerical aperture lens with three-zone annular phase pupil filter, vector diffraction method was applied to study the optical intensity distribution in transverse and axial directions. Numerical simulation results show that optical intensity distribution in transverse and axial directions need to be treated simultaneously. When three-zone annular phase pupil filter is added in front of a high numerical aperture lens, transverse super resolution, extended axial focal depth and flat-top focusing can be achieved at the same time. Furthermore, When phase modulation depth is changed, the phenomenon of axial focal shift can be found. The structure of three-zone annular phase pupil filter was optimized and the optimized results were given.

Phase is an important component of an optical wavefield bearing the information of the refractive index, optical thickness, or the topology of the specimen. Phase retrieval is a central problem in many areas of physics and optics since the phase of a wavefield is not accessible directly. The most well-established method for obtaining quantitative phase is through interferometry, such as digital holography. However, this class of methods relies on coherent illumination, therefore, plagued with problems of speckle that prevent the formation of high quality images. On a different note, quantitative phase can be retrieved by transport-of-intensity equation (TIE) using only object field intensities at multiple axially displaced planes. TIE has been increasingly investigated during recent years due to its unique advantages over interferometric techniques: it is non-interferometric, works with partially coherent illumination, computationally simple, no need to phase unwrapping, and does not require a complicated optical system. In this paper, we will review some recent new developments in TIE phase retrieval: including its numerical solution, treatment of boundary problem and the low-frequency artifacts, and configurations for dynamic phase imaging. We also reexamine TIE in terms of phase-space optics, demonstrating the effect of partially coherent illumination on phase reconstruction, and connecting it to light field imaging at the geometry optics limit. Published version