Effect of reflections on phase hologram recording in amorphous As-S-Se films

Experimental and theoretical studies of phase hologram recording in amorphous As-S-Se films with slightly wedge-shaped thickness profile are presented. It is shown that Fabry-Perot resonator effect caused by the interference of multiply reflected light beams inside the sample strongly changes the values of diffraction efficiency and its growth rate as well as the exposure time dependences of diffraction efficiency and transmissivity making them site-dependent and sample-dependent. Absorptivity and recording light intensity inside the sample are also significantly changed. The obtained results can be used to explain the holographic and optical experiments also in other materials with Fabry-Perot resonator effect such as other transparent thin films and photorefractive crystals.     

Speckle-free imaging of two-dimensional microscopic objects by holography

Schemes for recording and reconstruction of relief-phase reflection holograms providing virtually aberration-free imaging of the structure of two-dimensional objects were developed and substantiated. Samples of relief-phase reflection holograms forming a speckle-free image of a photolithographic test pattern with a characteristic size of 0.8 μm at a wavelength of 0.488 μm with a numerical aperture of 0.6 were obtained on a layer of recording medium (chalcogenide deposited on a plane glass substrate). On the basis of the results obtained, it was concluded that it is practically possible to attain the diffraction limit of hologram resolution and that further studies aimed at the implementation of methods of optical holography into photolithography and, predominantly, into short-wavelength ultraviolet lithography, are undoubtedly promising.     

Nanostructurization of thin chalcogenide glassy semiconductor films during formation of relief-phase hologram structures

The surface roughness of thin three-component chalcogenide glassy semiconductor (CGS) films during formation of relief-phase hologram structures has been investigated. It is established that the holograms formed on such films undergo parasitic surface nanostructurization, which determines their short-wavelength applicability limit. It is suggested that this structurization is caused by the initial cluster structure of a CGS film, which leads to spatial variations in its etching rate in a developer. It is shown that the maximum variations in the etch rate and cluster size are characteristic of unexposed areas of CGS films and that these variations significantly decrease with increasing exposure.

     

Charging of glassy chalcogenide semiconductors in corona discharge and its effect on holographic grating formation

Recording of optical holographic gratings based on photostructural transformations in thin (≈ 1 μm) As₂S₃ and As₂S₃ semiconductor layers in the presence and absence of a corona discharge and also chemical etching of these gratings are studied. Initiation of a corona at the stage of interference grating recording is shown to improve the exposure contrast of metal-glassy chalcogenide semiconductor thin-film structures. The holographic sensitivity, diffraction efficiency, dynamic range, and contrast are also improved severalfold. When phase relief gratings formed in these layers are selectively etched in a chemical etchant in the presence of a corona, their profile becomes more regular and deeper by 25–30% and the diffraction efficiency increases by 30–50%.     

双波长全息术实验研究及在自适应光学中的应用

在双波长全息术中,全息图可用一个波长记录,用另一个波长重现。用光学寻址液晶空间光调制器作为记录介质,可方便实现动态双波长全息图的记录。经一个畸变波前记录动态全息图后,由具有相同畸变的另一个波前去重现该动态全息图,可以实现对光学波前畸变的等比例缩小。在用于自适应光学的负性反馈回路中时,可简化大波前畸变的测量过程,可在中红外光谱范围内记录并制作动态全息图畸变校正器(在此波段直接的全息记录是极难的),也能增大可校正的畸变范围。介绍了这种动态干涉仪的实验实现,及该动态全息记录技术应用于自适应光学的前景。     

利用反射全息实现计算全息三维显示

计算全息和光学全息都可应用于三维显示,但各有自己的优势和缺陷.将计算全息和光学反射全息相结合,可以突破光学全息对记录物体的限制,进行虚拟物体或自然场景的全息图的制作,同时可以实现白光再现.本文首先用三维扫描仪获得实际物体的三维数据,用"点云算法"模拟得到其菲涅耳全息图透射率数据,采用计算全息打印机将其输出于全息记录介质,得到可光学再现的菲涅耳计算全息图H₁.然后将H₁作为光学全息的记录物体进行反射全息记录,将平面全息转化为体全息,实现了计算全息白光再现.     

Measurement of properties of silver telluride thin films using holography

Holography is an interferometric method of recording the light waves diffracted by a subject illuminated with coherent light. Holographic interferometry (H.I.) is one of the most important applications of holography. It is concerned with the formation and interpretation of fringe patterns, which appears when a wave generated at some earlier time and stored in a hologram is later reconstructed by interfering with comparison wave. We report a technique, which uses double exposure holographic interferometry together with simple mathematical interpretation, which allow immediate finding of stress and thickness of thin film. We tested the same for different normalities of solutions. It was further noticed that the fringe spacing changes with solution concentration as well as time of deposition. The thin films are prepared using electrodeposition technique. It’s structural, morphological and optical study carried out by XRD, SEM, and UV-Vis-NIR spectrophotometer.     

用体全息术对皮秒光脉冲进行二维测量

本文提供一种测量两束相干的ps光脉冲的空间二维时间振幅相关函数的新方法.在此方法中,光脉冲是被记录在一种光致折变的体积全息介质中,而所记录的信息可以通过直接量度在介质中所形成的光栅的空间分布而读出.这种方法可的可行性已为实验证实,它是通过3.5ps倍频锁模Nd:YAG激光测量光致折变晶体LiNbO₃来实现的。     

一种消除数字离轴全息零级像的实验方法

提出一种消除数字离轴全息零级像的实验方法.这种方法是将全息衍射光栅作为分光元件,形成数字离轴全息记录系统,通过调节记录光路系统中平面镜,改变物光波到达CCD的入射方向而引入相移,从而得到不同记录参数的全息图.再通过对不同记录参数全息图的数字处理,即可达到零级像消除的目的,并对这种方法进行了理论分析和实验验证.给出了利用这种方法获得的实验结果.实验结果证明了该方案的可行性,并且具有光路系统简单、操作和处理容易等特点.     

Influence of auxiliary violet light on holographic kinetics at low and high recording intensities in bacteriorhodopsin film

The photochromic bacteriorhodopsin (BR) film can be used as a rewritable holographic recording medium. Due to the saturation absorption and the scattering and reflecting lights from the BR film, the grating contrast-ratio of the hologram is diminished during the hologram recording. When the intensity of the recording light is low, the influence of the saturation absorption and the scatter and reflection of BR film on the grating contrast-ratio is weak. But for the case of intense recording light, this influence is more serious. It is found that the influence of the auxiliary violet light on the holographic kinetics of diffraction efficiency is distinct under different recording intensities. At the low recording light intensity, the steady diffraction efficiency is increased and the peak diffraction efficiency is suppressed by the auxiliary violet light. But for intense recording light, the steady diffraction efficiency and the peak diffraction efficiency are both increased by the auxiliary violet light. Based on the two-state model of BR photochromism, we give a good theoretical explanation to the above phenomena.     

Sensitive detection of phase and absorption gratings: Phase-modulated,homodyne detected holography

Phase-modulated holography (PMH) is a new technique for detecting very weak changes of the absorptivity or of the refractive index that occur in the course of an irreversible solid-state photoreaction. In contrast to conventional, phase-insensitive holographic techniques and to previous homodyne-detected holography, PMH allows to record the absorptive and dispersive hologram diffraction amplitudes separately and simultaneously, including their correct signs. PMH typically offers an up to eight orders of magnitude improvement of detection sensitivity over conventional techniques. These features render PMH an ideal tool for investigating new holographic recording materials, both for details of the underlying photoreaction and for the hologram formation mechanism.     

一种新型的彩色全息术

本文提出了一种彩色全息新方法。它只需用一种单一波长的激光器作全息照相光源,单色的全息干板作感光片,制得的全息图用白光透射再现。用三色圆,花束彩色目标做了实验,并给出了结果。 关键词：     

不同记录光强下辅助紫光对菌紫质薄膜全息衍射效率的影响

具有光致变色效应的菌紫质薄膜可用作可擦重写型全息记录介质. 在全息记录过程中,由于菌紫质薄膜对记录光的散射和反射引起记录光栅对比度下降,当记录光较弱时,这种影响较小,可以忽略;但当记录光较强时,散射和反射光对记录光栅的影响很大,必须考虑它们对光栅对比度的影响才能对实验结果进行合理的解释. 实验发现在不同的记录光强下辅助紫光对衍射效率动力学曲线的影响不同,当记录光强较弱时,加入辅助紫光可以提高衍射效率的稳定值、抑制峰值;而当记录光强较强时,加入辅助紫光除了提高衍射效率的稳定值外,还可以提高衍射效率的峰值. 关键词： 菌紫质 衍射效率 干涉条纹对比度     

利用偏振全息记录可重复擦写的偶氮相位光栅

利用偏振全息技术在偶氮苯侧链聚合物薄膜上进行了记录全息相位光栅的研究.从理论和实验两方面分析了不同的偏振全息模式、偶氮高分子聚合物材料和全息曝光时间对相位光栅生成的影响.通过实验比较,确定了最佳的实验条件,在形成折射率相位光栅的同时,最大限度的避免了由于大分子运动而导致的表面起伏对相位光栅的破坏,并在此基础上,记录了可重复擦写的全息相位光栅.这种全息光栅制作比较方便,光栅系数可以方便的调整,在室温下非常稳定并且能用圆偏振光完全擦除后重复写入.     

利用反射全息实现计算全息三维显示

计算全息和光学全息都可应用于三维显示,但各有自己的优势和缺陷.将计算全息和光学反射全息相结合,可以突破光学全息对记录物体的限制,进行虚拟物体或自然场景的全息图的制作,同时可以实现白光再现.本文首先用三维扫描仪获得实际物体的三维数据,用"点云算法"模拟得到其菲涅耳全息图透射率数据,采用计算全息打印机将其输出于全息记录介质,得到可光学再现的菲涅耳计算全息图H1.然后将H1作为光学全息的记录物体进行反射全息记录,将平面全息转化为体全息,实现了计算全息白光再现.     

A ballistic gravimeter with dropping holographic grating

The principle of operation of a ballistic laser gravimeter based on a dropping holographic diffraction grating is described. The free-fall acceleration of the grating is determined from a change in the frequency of beats that arise during the interference of light beams diffracted on the hologram in the zeroth and first orders of diffraction. An experiment demonstrating this principle of measurement is described. The main distinctive features of the proposed gravimeter are simple design, compact size, and the possibility of using this device for analysis of high-frequency fluctuations in the gravitational-field strength.     

Hologram recording in DuPont photopolymer films by use of pulse exposure

Reflection hologram recording in DuPont HRF-800X071-20 photopolymer films has been demonstrated by use of pulsed laser exposure with pulse lengths of 25 ns. An expected weak reflectance of the recorded mirror holograms could be significantly increased by preillumination. Although pulsed preillumination enhanced only the reflectance, continuous incoherent preillumination significantly increased both the diffraction efficiency (which reached ~80%) and the sensitivity (which reached an increase of ~100 times, thus approaching the sensitivity of cw recording). The results are compared with those for hologram recordings obtained with cw exposure under the same processing conditions. Spectral absorbance curves of recorded holograms are presented, and possible mechanisms of hologram formation are discussed.     

A study of preparation techniques and properties of bulk nanocomposites based on aqueous albumin dispersion

It is established that DNA films sensitized by organic dyes (for example, acridine orange), subjected to pulsed excitation in the dye absorption band, allow for several types of time-dependent holographic recording. Dynamic holographic gratings on the dye triplet states and thermal and relief-phase holographic gratings of nondestructive type have been recorded. The efficiency and lifetime of these gratings depend strongly on the concentration of dye, the type of its bonding with the biopolymer, and the recording-pulse energy. High-efficiency relief holographic gratings formed due to the structural transformations occurring in the biopolymer matrix when the energy of recording laser pulses dissipates into heat spontaneously and completely (or almost completely) disappear with time at room temperature. Some data on the distribution of acridine orange molecules over binding sites in the DNA matrix are obtained.     

Dynamics of pulsed recording of holographic diffraction gratings in photopolymer materials

The dynamics of recording holographic diffraction gratings in photopolymer material using 10-ns pulses of Nd:YAG laser radiation (532 nm) was investigated. The formation of permanent and intermediate gratings was observed. Optimization of the photopolymer composition for pulsed recording was performed. The kinetic photopolymerization models taking into account the mechanisms of radical destruction due to recombination and by impurities are verified. Measurement of the recording kinetics at different recording angles showed that diffusion does not affect the hologram formation for times of the same order of magnitude as the recording duration (0.1 s) at a length of the grating half-period. Samples of the photopolymer composition in triethanolamine were investigated and diffusion of oligomeric acrylamide molecules was revealed. The diffusivity was found to be 1.1 × 10^?9 cm²/s.     

光热折变体光栅变波长读出特性及稳定性研究

光热折变体光栅是在光敏玻璃材料中利用光热折变效应记录的折射率型体全息光栅,具有波长和角度选择性好、衍射效率高、热稳定性好和抗损伤阈值高等特点,在激光器技术领域中具有独特的优势。在自行制备的光敏玻璃材料中,用325nm波长的紫外光曝光记录透射型体全息光栅,基于变波长读出的原理设计实验,对热显影后的光热折变体光栅在532nm波长的激光照射下的衍射读出特性以及其在恒定光功率密度的激光照射下的稳定性进行了实验研究。研究结果表明,热显影后的光热折变体光栅在激光辐照下具有光致饱和效应。根据实验结果定量计算出了光热折变体光栅的选择角和描述光致饱和效应的特征时间常数。