大角带宽高衍射效率体全息光栅的设计和制备

高性能体全息光栅是全息波导的重要耦合元件,角带宽小、平均衍射效率不高是制约体全息光栅性能的重要因素.以不对称倾斜记录为出发点,设计并制备了大角带宽高衍射效率的体全息光栅.首先讨论在横电模式光和横磁模式光下体全息光栅的记录参数与其衍射效率的关系,找到平均衍射效率较高的记录参数范围,随后进一步分析在此范围内的记录参数与体全...     

Diffraction properties of ultrashort pulsed beams with arbitrary temporal profiles by a reflection volume holographic grating

The diffraction properties of reflection volume holographic gratings are studied when the gratings are illuminated by an ultrashort beam with arbitrary temporal profiles. The modified Kogelnik's theory of coupled waves is used. Simple analytical expressions for spectral and temporal distribution of the transmitted and diffracted are obtained. The dependences of the diffraction bandwidth, the Bragg selectivity bandwidth and the total diffraction efficiency of the reflection volume grating on the temporal profiles of the input ultrashort pulse are investigated. Study shows that the bandwidth of the reflection volume holographic gratings varies with the grating parameters more slowly than the transmitting volume holographic gratings. For three different temporal profiles, numerical results about diffraction properties of the reflection volume holographic gratings are given and compared with the transmitting volume holographic gratings.     

Pixel size limit in holographic memories

The bandwidth of holographic recording in LiNbO(3) (Fe doped) in the 90 degrees geometry is studied theoretically and experimentally. The wide holographic bandwidth of LiNbO(3) makes it possible to record submicrometer pixels and reconstruct them by phase conjugation in a holographic memory system. This approach reduces the system cost and increases the system storage density. We demonstrate the recording and the phase-conjugate reconstruction of various pixel sizes down to 1 mumx1 mum . The signal-noise ratio and the bit-error rate are examined.     

Light diffraction from the volume holograms in electrooptic birefringent crystals

Angular bandwidth of the image reconstructed from the volume phase hologram at a wavelength different from that of the recording beams has been analysed. An optimum holographic scheme on the basis of anisotropic diffraction uniting maximum bandwidth of the Gabor's scheme and advantages of the Leith-Upatnieks scheme has been proposed for non-destructive readout of the volume hologram in birefringent photorefractive crystals. The main results of the theoretical analysis leading to the optimum holographic arrangement for electrically controlled retrieval of information from the volume of the electrooptic crystal are presented. Demonstrating experiments has been performed with LiNbO₃: Fe crystals.     

反射式窄带全息滤光片

根据耦合波理论,体积全息图有很好的滤光特性,可以作为一种窄带滤光片在实际中得到应用.本文针对峰值波长、带宽和衍射效率这三个主要参数讨论了全息滤光片的性质,提出了全息滤光片的设计步骤,并指出了全息滤光片的特点及应用前景.     

Reconstruction resolution enhancement of EPISM based holographic stereogram with hogel spatial multiplexing

We investigate how the splicing mode of a holographic element (hogel) affects the reconstruction of a 3D scene to improve the reconstruction resolution of a holographic stereogram fabricated using the effective perspective image segmentation and mosaicking method (EPISM). First, the effect of hogel spatial multiplexing on holographic recording and reconstruction is studied based on the mechanism of recording interference fringes in the holographic recording medium. Second, combined with the influence of multiple exposures on the hologram's diffraction efficiency, the diffraction efficiency of the holographic stereogram is analyzed in the spatial multiplexing mode. The holographic stereogram is then regarded as a special optical imaging system. The theory of spatial bandwidth product is adopted to describe the comprehensive resolution of the holographic stereogram, which explains why hogel spatial multiplexing can significantly improve the reconstruction resolution of a holographic stereogram. Compared with the traditional printing method under the same parameters in optical experiments, hogel spatial multiplexing has a lower diffraction efficiency but a higher quality of reconstructed image, consistent with the theoretical analysis.     

Material characterization by holographic methods

After an introduction to the theoretical fundamentals, different holographic techniques for material characterization are presented: Isotropic and anisotropic diffraction measurements, interferometric techniques, holographic microphotometry, isotropic and anisotropic holographic scattering and self-diffraction experiments, beam-coupling topography and neutron holography.     

平显全息组合镜的衍射特性研究

给出了平显用全息组合镜的衍射效率、水平选择角和带宽的实验测量结果,并运用耦合波理论进行了分析.测试结果表明,DCG是一种制作体积全息图的优良材料,由其制作的全息组合镜具有优良的透过率和衍射特性.     

彩虹全息图和普通全息图的空间频率带宽

本文从菲涅耳-基尔霍夫衍射理论出发,从单狭缝彩虹全息图入手,具体分析了物、狭缝、参考光源及全息片在不同相对位置时全息图的空间频率带宽,得出了在各种情况下对彩虹全息图和普通全息图都普遍适用的统一公式,为在实际应用中压缩空间频率带宽及胶片选取、了解全息图对目标的空间频率损失提供理论上的根据。 关键词：     

新型透射式全息窄带带阻滤光器的光谱特性分析

滤光器在光谱学、光学测量和激光物理中有着极其重要的应用。全息滤光器是一种新型滤光器,特别是利用重铬酸明胶(DCG)记录的全息透射式窄带滤光器,其主要特点为对主谱线有很窄的带宽。文章主要用紫外-可见分光光度计测定用DCG记录的透射式全息窄带带阻滤光器的光谱特性,测量结果分析表明,滤光器在可见光区域(400～800 nm)对其中心波长的相对透射率小于2%,其他谱线的相对透射率大于85%。且滤光器有较窄的带宽,其半宽度小于12 nm,十分之一宽度小于15 nm。对氩离子激光(Ar+)主谱线514.5 nm有优良的滤光特性。     

Ultrafast holographic Stokesmeter for polarization imaging in real time

We propose an ultrafast holographic Stokesmeter using a volume holographic substrate with two sets of two orthogonal gratings to identify all four Stokes parameters of the input beam. We derive the Mueller matrix of the proposed architecture and determine the constraints necessary for reconstructing the complete Stokes vector. The speed of this device is determined primarily by the channel spectral bandwidth (typically 100 GHz), corresponding to a few picoseconds.     

新颖材料器件为全息显示带来的新机遇

三维显示是人类获取身临其境视觉信息的有效途径,其中全息技术能够提供人眼所需的全部深度信息,被认为是理想的三维显示方式.然而受目前显示器件的限制,如可刷新调制器件的时间-空间(时空)带宽积受限、海量数据云处理速率限制、图像质量不高的问题等,全息显示技术的发展进入了瓶颈期.为了提高显示质量、扩大时空带宽积、提升系统性能,需要发展崭新的全息显示器件,从根本上解决目前遇到的问题.超颖材料、超构表面以及二维材料等诸多新颖材料的涌现为全息显示带来新的机遇.超颖材料(表面)通过特殊设计,利用远小于波长的超构单元实现对波前各向同性或各向异性的振幅与相位的特异调控,进而将全息信息映射到超颖材料(表面)全息显示器件上,通过调控光波实现各种显示.发展可刷新的超构(表面、二维)材料并应用于动态全息显示中是未来的重要方向.虽然现有的新颖器件还面临着各种问题,但它们可为全息显示的发展提供潜在的可行性和新的视角与发展动力.     

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.     

反射型体全息光栅对超短脉冲激光光束衍射的性质

在光栅记录介质色散效应的影响下,拓展Kogelnik的耦合波理论研究了反射型体全息光栅对偏振方向垂直和平行于入射面的超短脉冲激光光束衍射的性质。结果表明对于记录在LiNbO3光折变晶体中的体全息光栅,在色散效应、光栅参量和入射条件的共同影响下,光栅对偏振方向垂直于入射面的超短脉冲激光光束衍射的光谱带宽大于对偏振方向平行于入射面的超短脉冲激光光束衍射的光谱带宽,在不考虑光栅介质色散效应的影响时,它们都变大。进一步给出了衍射光的光谱带宽及光栅的衍射效率随入射脉冲的光谱带宽与光栅的光谱带宽比值的变化情况。     

Le facteur de qualite N/τ dans les deflecteurs de faisceaux lasers: Comparaison entre deflecteurs holographiques et acousto-optiques

N/τ (number of addressable points divided by access time) is a valuable figure of merit for laser scanners. It is shown that N/τ has the same theoretical expression for both acousto-optic and holographic scanners, and that it depends on the bandwidth of the temporal phenomenon “displacement of the fringes in the pupil” as well as on the nature of the scanning (continuous or discontinuous, with or without focusing). The comparison between acousto-optic and holographic scanners show clearly the interest of the latter. The bidimensional character of holographic scanning is probably its main advantage, for it is very convenient and it augments the number of points N: for holographic scanners, N and even N/τ can reach higher values than for acousto-optic scanners.     

Tunability of nonuniform reflection holographic filter

The tunability of nonuniform reflection holographic filter is investigated theoretically and experimentally. It is shown that the reflection holographic filter has not only high optical density and narrow bandwidth, but also good tunability. The coupled wave theoretical model for uniform medium is compared with the model for nonuniform medium. It is identified that the coincidence of the theoretical results of the nonuniform model with the experimental results are better than that of the uniform model.     

非均匀反射体全息窄带带阻滤光片

在实验基础上,利用非均匀耦合波理论得出了介质折射率调制度和空频变化的非均匀模型,利用此模型分析了窄带宽和高光学密度滤光片所应具有的非均匀分布特性,指出了实验工艺上应努力的方向,实验上用重铬酸明胶（DCG）实现了性能优良的高光学密度窄带宽的全息带阻滤光片,峰值波长光学密度为4－5,半宽度小于20nm.     

Linewidth and coherence properties of scattered light

The holographic recording of light scattered by brownian particles is discussed. It is shown that, due to the finite time of exposure, the record acts as a temporal filter of non-zero bandwidth. As a consequence the holographic recording can be obtained in spite of the frequency change of the scattered light. The experimental results show that, in fact, such a procedure can constitute an alternative way to measure the linewidth of the scattered light.     

Determination of optical field generated by a microlens using digital holographic method

In the paper, application of the digital holographic method for full field characterization of the beam generated by microlenses is considered. For this goal, the laboratory setup was designed based on Mach-Zehnder interferometry with the additional reference channel. The beam generated by a microlens was imaged by an afocal system and intensity distributions or interferograms (holograms) were registered by CCD camera. The digital holography using one image allows us to determine microlens parameters, i.e., focal length, aberrations, and shape. The optimum conditions to determine the surface shape of a microlens using holographic method have been found. We compare obtained results with geometrical and interferometric measurements. We show the advantage of digital holography for a shape microlens determination (improved accuracy), aberrations, and focal length (characterization facility). Through optimum refocusing, the digital holography gives more precise shape. The paper is accompanied with computer simulations and the experimental measurement data for geometrical, interferometric, and holographic methods.     

Study on the simplified phase-shifting digital holographic microscopy

In this paper, a new simplified technique for effectively eliminating the zero order and the conjugate virtual image in digital holographic microcopy, which makes use of two-step phase-shifting method of just recording two holograms and an intensity image of object wave, is proposed. Meanwhile, combined with the principle of making full use of spatial bandwidth of the CCD sensor by in-line lens-less Fourier holographic recording geometry, the theory and experimental methods to increase the resolution of the reconstructed image in digital holography by using phase-shifting technique are detailedly analyzed. At end, the validity and availability of this technique has been demonstrated through the off-axis and in-line Fourier transform recording geometry. The study provides some theoretical and experimental guidance for the design and operation of a digital holographic microscopy system.