Analysis and Prediction of Effect of Turning Marks Diffraction on Image Quality of Optical System

Single-point diamond turning (SPDT) is widely used in the machining of infrared materials and metal-based mirrors. Diamond tips can scratch material, replicate the shape of the tip, and create annular turning marks on optical surfaces, which can have unpredictable adverse effects on imaging. In order to predict the effect of turning marks diffraction on the degradation of imaging quality, a model of the influence of SPDT processing parameters on the reduction of system imaging MTF under the influence of ideal grating turning marks diffraction was established. The results show that the depth of the turning mark will lead to the decline of MTF, especially the low frequency information. Finally, a method is proposed to reduce the effect of turning marks diffraction through changing the processing parameters. .

Design of Time-Resolved Shifted Dual Transmission Grating Spectrometer for the X-Ray Spectrum Diagnostics

A new time-resolved shifted dual transmission grating spectrometer （SDTGS） is designed and fabricated in this work. This SDTGS uses a new shifted dual transmission grating （SDTG） as its dispersive component, which has two sub transmission gratings with different line densities, of 2000 lines/mm and 5000 lines/mm. The axes of the two sub transmission gratings in SDTG are horizontally and vertically shifted a certain distance to measure a broad range of 0.1-5 keV time-resolved X-ray spectra. The SDTG has been calibrated with a soft X-ray beam of the synchrotron radiation facility and its diffraction efficiency is also measured. The designed SDTGS can take full use of the space on a record panel and improve the precision for measuring spatial and temporal spectrum simultaneously. It will be a promising application for accurate diagnosis of the soft X-ray spectrum in inertial confinement fusion.

DEFORMATION MEASUREMENT USING DUAL-FREQUENCY PROJECTION GRATING PHASE-SHIFT PROFILOMETRY

2π phase ambiguity problem is very important in phase measurement when a deformed object has a large out of plane displacement. The dual-frequency projection grating phaseshifting profilometry （PSP） can be used to solve such an issue. In the measurement, two properchosen frequency gratings are utilized to synthesize an equivalent wavelength grating which ensures the computed phase in a principal phase range. Thus, the error caused by the phase unwrapping process with the conventional phase reconstruct algorithm can be eliminated. Finally, experimental result of a specimen with large plastic deformation is given to prove that the proposed method is effective to handle the phase discontinuity.

Single order soft X-ray diffraction with quasi-random radius pinhole array spectroscopic photon sieves

A novel single order diffraction grating in the soft X-ray region, called quasi-random radius pinhole array spectro- scopic photon sieves （QRSPS）, is proposed in this paper. This new grating is composed of pinholes on a substrate, whose radii are quasi-random, while their centers are regular. Analysis proves that its transmittance function across the grating bar is similar to that of sinusoidal transmission gratings. Simulation results show that the QRSPS can suppress higher-order diffraction effectively. And the QRSPS would still retain its characteristic of single order diffraction when we take the effect of X-ray penetration into account. These properties indicate that the QRSPS can be used in the soft X-ray spectra measurement.

Dynamic analysis of holographic gratings in a multi-wavelength visible light sensitive photopolymer

A dynamic theoretical model of photochemistry and hologram formation in holographic photopolymer is established, and the dynamic development process of holographic gratings in the photopolymer is discussed with the model. A novel multi-wavelength visible light sensitive photopolymer for holographic storage is prepared. The influence of exposure wavelength on holographic storage characteristics is analysed. By fitting the experimental data of transmittance and diffraction efficiency to a function of time with different exposure intensities and wavelengths, the variations of dynamic parameters of photochemistry and photopolymerization diffusion are presented.

Diffraction of an ultrashort pulsed beam with arbitrary polarization state from a volume holographic grating in LiNbO3 crystals

Based on a modified coupled wave theory of Kogelnik, we have studied the diffraction of an ultrashort pulsed beam with an arbitrary polarization state from a volume holographic grating in photorefractive LiNbO3 crystals. The results indicate that the diffracted intensity distributions in the spectral and temporal domains and the diffraction efficiency of the grating are both changed by the polarization state and spectral bandwidth of the input pulsed beam. A method is given of choosing the grating parameters and input conditions to obtain a large variation range of the spectral bandwidth of the diffracted pulsed beam with an appropriate diffraction efficiency. Our study presents a possibility of using a volume holographic grating recorded in anisotropic materials to shape a broadband ultrashort pulsed beam by modulating its polarization state.

OPTICAL STORAGE MECHANISM AND HIGH-ORDER DIFFRACTION PROPERTIES OF NITROAZOBENZENE-CONTAINING POLYESTER FILMS

Using Nd:YAG second harmonic pulse (100 ps), the optical storage properties of two novel polyesters, poly [4'-bis (N, N-oxyethylene) imino-4-nitroazobenzene succinyl] and poly [2'-chloro-4'-bis (N, N-oxyethylene) imino-4-nitroazobenzene succinyl] have been studied by multiwave mixing. The high-order diffractions of the orientation gratings induced by anisotropy via the reorientation of nitroazobenzene groups and optical information storage with long-term stability have been realized by multiwave mixing in their films. Up to 3rd order forward diffraction was detected in two wave mixing, while up to 4th order backward diffraction was observed in degenerated four wave mixing. The recording mechanism was explained by the trans-cis-trans isomerization cycles of azobenzene groups. The isomerization of these azobenzene groups probably undergoes with inversion mechanism under the experimental conditions. The information recorded in these films has been kept for more than 6 months.

Analysis of restriction factors of widening diffraction bandwidth of multilayer dielectric grating

In order to design a multilayer dielectric grating with wide-bandwidth diffraction spectrum, the restriction factors of both the reflection bandwidth of multilayer dielectric high-reflectivity mirror and the guided-mode resonance phe- nomenon are studied in detail. The reflection characteristics of high-reflectivity mirror in zeroth and -lst transmitted diffraction orders are quantitatively evaluated. It is found that the reflection bandwidth of high-reflectivity mirror in -lst transmitted diffraction order, which determines the final diffraction bandwidth of multilayer dielectric grating, is evidently compressed. Furthermore, it is demonstrated that the reducing of grating period is an effective approach to the elimination of guided mode resonance over a required broad band range both spectrally and angularly. In addition, the expressions for calculating the maximum period ensuring no guided mode resonance in the required bandwidth are derived. Finally, two high-efficiency pulse-compression gratings with broad-band are presented.

Diffraction Pattern of a Rotated Grating

Diffraction patterns of a rotated grating are investigated from both theoretical and experimental points of view. It is shown that as the grating rotates, the angle of deviation of each diffracted line relative to the incident light goes through a minimum, and that the angle between any two successive diffracted lines goes through a minimum value which is the same for all adjacent diffracted lines. It is also shown that the angle between diffraction lines with n=1 and n=-1 is not sensitive to small variations of the grating from being normal to the incident light. Finally, a method is suggested for determining the line distance of a diffraction grating with high accuracy.

Optical diffraction gratings embedded in BK-7 glass by low-density plasma formation using femtosecond laser

The optical embedded diffraction gratings with the internal refractive index modification in BK-7 glass plates were demonstrated using low-density plasma formation excited by a high-intensity femtosecond （130 fs） Ti： sapphire laser （λp=790 rim）. The refractive index modifications with diameters ranging from 400 nm to 4 gm were photoinduced after plasma formation occurred upon irradiation with peak intensities of more than 1 ×10^13 W/cm2. The graded refractive index profile was fabricated to be a symmetric around the center of the point at which low-density plasma occurred. The maximum refractive index change （An） was estimated to be 1.5x10 2. Several optical embedded gratings in BK-7 glass plate were demonstrated with refractive index modification induced by the scanning of low-density plasma formation.

LO-RAY-LIGH@ Diffraction Gratings in UV-VIS Spectroscopy

It has been more than half a century since the release of the first Shimadzu UV-VIS （UV-visible） spectrophotometer QB-50 in 1952, and during this time more than 160,000 UV-VIS spectrometers have been produced and installed in a wide variety of different applications. A lot of technical innovations have been implemented to improve the performance and significantly reduce the stray light levels. The latest innovation during development of sophisticated spectrophotometers is based on a new holographic exposure method and optimized etching process which has made it possible to produce both high-efficient and exceptionally low stray light gratings. These LO-RAY-LIGH~ gratings have guaranteed values of stray light at the intermediate position between zero-order and first-order lights. The values are measured by Shimadzu＇s laser stray-light-measuring system. The latest development in the series of UV-VIS spectrophotometers is the UV-2700 which is a true double beam double monochromator system in a compact design for high-precision spectral analysis of a wide range of samples including organic and inorganic compounds, biological samples, optical materials and photovoltaics. The high performance optical system is designed with ＂LO-RAY-LIGH＂ diffraction gratings, featuring highest efficiency and exceptionally low stray light. The spectrophotometer operates in the wavelength range from 185 nm to 900 nm and allows highly sophisticated applications such as direct measurement of high density samples up to 8 absorbance units without dilution.

The Design and Manufacturing of Diffraction Optical Elements to form a Dot-Composed Etalon Image within the Optical Systems

The possibilities of manufacturing of diffraction optical elements (DOE), using the “Caroline 15 PE” plasma-etching machine were considered. It is established that at thickness of chromic mask of 100 nm the plasma-chemical etching (PCE) method reaches depth of surface micro-profile to 1.4 μm on optical glass. It allows increasing the diffraction efficiency of DOE to 0.3 - 0.35 on the second order of diffraction.

Bragg-Angle Diffraction in Slant Gratings Fabricated by Single-Beam Interference Lithography

A single-beam interference-lithography scheme is demonstrated for the fabrication of large-area slant gratings, which requires exposure of the photoresist thin film spin-coated on a glass plate with polished side-walls to a single laser beam in the ultraviolet and requires small coherence length of the laser. No additional beam splitting scheme and no adjustments for laser-beam overlapping and for optical path-length balancing are needed. Bragg-angle diffractions are observed as strong optical extinction that is tunable with changing the angle of incidence. This device is important for the design of efficient filters, beam splitters, and photonic devices.

Study of transmission grating diffraction efficiencies for soft X-ray

Tansmission grating spectrometers are extensively used to measure absthlute X-ray spectra in a photon-energy range below 1000 eV. The transmission grating,as its dispersive element, must be calibrated to obtain its danaction efficiencies. Calibrations of absolute distraction efficiencies of the tlansmission grating at photon energyof 844eV have been carried out on Beliing Synchrotron mediation Facility. With theaid of grating model, all of the grating structure paraxneters have been determinedand the absolute dchaction efficiencies in a photon-energy range below 2000eV havealso been calculated and discussed.

Theory and method of dual-energy x-ray grating phase-contrast imaging

The principle of dual-energy x-ray grating phase-contrast imaging(DEPCI) is clarified by using the theory of x-ray interference and Fresnel diffraction. A new method of retrieving phase from the two interferograms is proposed for DEPCI,and its feasibility is verified via simulation. Finally, the proposed method applied to DEPCI experiment demonstrates the effectiveness of the method. This paper lays the theoretical foundation for performance optimization of DEPCI and the further integration of DEPCI and computed tomography.

Measurement of a discontinuous object based on a dual-frequency grating

The dual-frequency grating measurement theory is proposed in order to carry out the measurement of a discontinuous object. Firstly, the reason why frequency spectra are produced by low frequency gratings and high frequency gratings in the field of frequency is analysed, and the relationship between the wrapped-phase and the unwrapping-phase is discussed. Secondly, a method to combine the advantages of the two kinds of gratings is proposed： one stripe is produced in the mutation part of the object measured by a suitable low frequency grating designed by MATLAB, then the phase produced by the low frequency grating need not be unfolded. The integer series of stripes is produced by a high frequency grating designed by MATLAB based on the frequency ratio of the two kinds of gratings and the high frequency wrapped-phase, and the high frequency unwrapping-phase is then obtained. In order to verify the correctness of the theoretical analysis, a steep discontinuous object of 600×600 pixels and 10.00 mm in height is simulated and a discontinuous object of ladder shape which is 32.00 mm in height is used in experiment. Both the simulation and the experiment can restore the discontinuous object height accurately by using the dual-frequency grating measurement theory.

基于Mathematica的平行光斜入射光栅衍射的模拟和可视化研究

光栅衍射作为大学物理的重要教学内容和教学难点,由于其理论推导和数学表达形式复杂,学生难以形成清晰的物理图像,导致课堂教学效果不理想。教材中仅对光垂直入射光栅时的衍射特性进行了讨论,但平行光斜入射光栅时的衍射特性却未被充分探讨,且这一领域的研究仍然有限。本文首先应用光的衍射理论推导出了平行光斜入射条件下单缝衍射和光栅衍射的光强分布表达形式,将单缝衍射和光栅衍射的研究由垂直入射推广到斜入射的情况。然后,应用Mathematica软件中的强大的交互式界面Manipulate,结合Initialization和Limit命令,对平行光斜入射情况下的单缝衍射和光栅衍射的光强分布进行了系统的模拟和仿真,分别绘制出单缝衍射的相对光强分布、多缝干涉的相对光强分布、光栅衍射的相对光强分布和衍射条纹分布情况。通过可视化过程,使学生深刻地理解光栅衍射的光强分布是单缝衍射和多缝干涉共同作用的结果,单缝衍射提供了光强分布的包络,而多缝干涉则决定了衍射条纹的具体亮暗变化,将抽象的光的衍射现象形象直观地动态演示出来,这有助于学生建立清晰的物理图像,深刻地理解单缝衍射和光栅衍射,极大地提高教学效果。

基于矢量衍射理论的光栅干涉仪位移测量误差研究

光栅干涉仪位移测量系统作为测量领域中最精密的测量仪器之一,由于在测量过程中光栅的姿态位置无法保证完美装配,使得光栅的光栅矢量方向与运动矢量方向之间出现偏差,导致位移测量结果出现周期性非线性误差。文中针对在光栅干涉仪位移测量过程中出现的光栅与位移台以及读数头之间的姿态位置误差进行分析,通过分别建立位移坐标系及光栅坐标系,参考惯性导航领域中飞行器姿态表示方法,利用一维光栅的横滚、俯仰和偏航角共同描述一维光栅相对于位移台的装配状态。通过基于矢量衍射理论分析光栅干涉仪位移测量时三个维度的角度偏差量,对可能产生的位移测量误差进行了分析说明。基于广义一维光栅方程,探究出了一个更为普遍的结论,为后续装置的改进提供理论依据,以提高系统的测量精度。

高边缘视场光学效率的衍射波导准直投影镜头设计

随着微型发光二极管(micro-light emitting diode,Micro-LED)微型图像源被应用于增强现实(augmented reality,AR)显示技术,AR显示系统朝着超小型化方向发展。然而Micro-LED图像源发光角度大,准直投影镜头要求体积小且像质高,其产生的渐晕现象也导致视场(field of view,FOV)边缘处光学效率低、照度不均匀,这对AR光学系统设计造成了挑战。为了解决上述问题,该文基于增加计算得到的非球面场镜,设计了一种照度均匀性高、边缘视场光学效率较高的衍射光栅波导准直投影镜头。对场镜理论进行详细分析,从而确定焦距区间,最终求解其面型参数,设计出照度相对均匀的镜头。设计的新型准直投影镜头对角线FOV为41.2°,F#为1.87,调制传递函数在125 lp/mm处大于0.5。仿真结果表明,系统照度均匀性相对提高了14%,边缘FOV的光学效率相对提高了15%,具有良好的成像性能,该镜头可应用于超小型AR衍射光栅波导头戴显示系统中。

光折变晶体中平面光栅的构建与研究

光折变效应在全息存储和处理方面具有重要的应用价值,光折变晶体中的全息光栅特性直接影响信息处理的质量和速度.本实验通过理论分析,计算得出Raman-Nath平面光栅的制作参量,设计实验系统并测量了LiNbO 3晶体中平面光栅的多级衍射性质,讨论了多级衍射效率和其空间分布特征.实验设计基于学生的光学知识和实验技能,向非线性光学知识和科学思辨创新方法拓展,在可调光分束器、图像处理等方面具有潜在的应用价值.