利用菌紫质薄膜进行角度复用和偏振复用全息存储实验研究

全息光存储以其高密度、大容量、高速并行数据存取而成为光存储领域的一个重要研究方向。生物光致变色材料———菌紫质是一种新型可擦重写全息记录介质。实验证明了使用菌紫质薄膜进行角度复用和偏振复用全息存储的可行性。利用菌紫质的光致变色特性,采用90°角度复用全息存储光路,在BR-D96N薄膜样品同一位置上实现了6幅全息图存储,并分别读出了无串扰的再现像。利用菌紫质薄膜的光致各向异性进行了偏振复用全息存储,在BR-D96N薄膜样品的同一位置上存储了两幅正交偏振光记录的图像,用原参考光再现和偏振片选择,可分别读出这两幅图像。     

吲哚俘精酰胺的偏振全息图像光存储实验研究

在吲哚俘精酰胺/PMMA薄膜上记录了同偏振全息和正交偏振全息图，获得了它们的再现衍射像.实验结果表明：吲哚俘精酰胺具有光致各向异性，可以进行正交偏振全息记录.在偏振全息中，衍射光的偏振方向依赖于物光和再现光的偏振方向，衍射像的噪声主要来源于再现光照射到样品上引起的散射.正交偏振全息可以得到比同偏振全息更高信噪比的衍射像.存储于样品上的全息图在室温下黑暗处至少可以保存五个月而衍射效率无明显下降.结果表明，吲哚俘精酰胺是一种可用于偏振全息的可擦重写记录介质. 关键词： 偏振全息 光致各向异性 俘精酸酐 光致变色     

辅助紫光提高菌紫质全息衍射效率的实验和理论研究

由于菌紫质样品的饱和吸收特性，在全息记录中，当记录光强大于样品的饱和光强时，全息光栅透过率随记录光相位差的分布远离余弦型，因此衍射效率的稳定值很低.菌紫质样品在红光和紫光共同作用下存在着双光束互补抑制效应，紫光可以抑制红光的透过率，提高红光的饱和光强，使记录区域由非线性区移至线性区，从而使全息光栅透过率随记录光相位差的分布变为余弦型，可以有效地提高全息衍射效率.实验证明，辅助紫光大大提高了菌紫质样品全息衍射效率的稳定值.根据此原理，建立了三光束全息光存储系统，在红光记录全息图的同时加入辅助紫光，可以使全息图衍射效率及衍射像的像质得到提高. 关键词： 菌紫质 全息存储 衍射效率 饱和吸收     

紫光诱导菌紫质中同圆偏振光栅的衍射调制特性

基于琼斯矩阵和菌紫质分子光循环的简化光循环模型,建立了紫光诱导同圆偏振记录光栅的理论模型,采用四波耦合光路测量菌紫质光栅的衍射效率.理论模拟和实验结果表明:加入线偏振的辅助紫光,线偏振再现光与线偏振辅助紫光相互平行时,菌紫质光栅的衍射效率最大;线偏振再现光与线偏振辅助紫光相互垂直时,菌紫质光栅的衍射效率最小;菌紫质薄膜中同圆偏振记录光栅的稳态衍射效率随线偏振再现光偏振方向和线偏振辅助紫光偏振方向之间的夹角按余弦规律变化.线偏振紫光能诱导同圆偏振记录光栅由非偏振光栅转化为偏振光栅.     

菌紫质同线偏振全息记录时再现光偏振方向对衍射效率的调制

当用相同偏振方向的物光和参考光在菌紫质薄膜上记录光栅时,再现光的偏振方向会影响其衍射效率.采用琼斯矩阵方法对此进行了理论分析,结果显示,再现光的偏振方向对衍射光的光强产生余弦调制;当再现光的偏振方向平行或垂直于记录光的偏振方向时,衍射光仍为线偏振光,其他情况下衍射光均变成椭圆偏振光.再现光偏振方向对衍射效率峰值的调制为正向余弦调制,对衍射效率稳定值的调制为反向余弦调制(与前者在相位上相差π).加入辅助紫光可抑制光栅的饱和,从而使得再现光偏振对衍射效率稳定值的调制由反向余弦调制变为正向余弦调制,并且提高了衍 关键词： 菌紫质 光致各向异性 衍射效率 琼斯矩阵     

偏振敏感材料中具有圆各向异性的偏振全息光栅

在向列相液晶中掺杂质量分数约0.2%的偶氮侧链型聚合物制成偏振敏感材料,使用正交圆偏振光记录了具有圆各向异性的一维偏振全息光栅,用线偏振光探测偏振全息光栅,得到正,负一级衍射光也为线偏振光,且偏振态与探测光和零级偏振态相互正交,可以运用琼斯矩阵理论加以解释.偏振全息光栅可由外加电场控制衍射级的变化,即在外加电场作用下,正、负一级衍射产生了90°的相位差.在频率6.05 Hz、电压2.2 V的外场作用下,衍射级的极值振荡变化.     

基于菌紫质F态的永久光存储研究

在线偏振飞秒激光激发下, 菌紫质通过双光子光化学反应可以生成具有永久光致各向异性的蓝移产物F₅₄₀态. 基于F₅₄₀态的永久光致各向异性, 通过调控飞秒激光空间光场分布, 可以在菌紫质薄膜中实现永久光信息存储. 本文使用纯相位型空间光调制器调制飞秒激光光场, 在物镜焦平面上生成光学点阵图案, 可以将信息快速记录在菌紫质薄膜中. 同时, 通过改变入射激光偏振方向, 可以实现偏振复用光存储, 这在高密度光存储和数据加密领域具有潜在应用.     

BR-D96N薄膜共线全息图像存储实验研究

利用一种生物光致变色材料—基因突变菌紫质BR-D96N薄膜的光致变色特性,实现了可擦写式共线全息图像存储实验.对于光密度为3.0的BR-D96N薄膜,在700mW/cm2的记录光强下(波长为632.8nm,物光、参考光光强比为约1∶1.2),全息图建立的最佳曝光时间约为3s,最佳再现光强约为50mW/cm2,全息图寿命约为10min.实验表明:共线全息存储技术光学系统简单,系统体积小,受存储环境的影响低,并能够实现高密度存储;同时也实验验证了BR-D96N薄膜具有响应速度快,感光灵敏度高,擦写次数高,稳定耐用,使用方便等优点,可以作为一种较灵敏的可擦写共线全息记录介质.     

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     

偏振控制的光折变开关

提出了两种模式偏振控制的光折变开关，推导了用非常偏振和寻常偏振光读出时的全息光栅的衍射效率比公式，该公式表明全息的衍射效率与偏振有关，衍射效率比可达８０％～９０％，利用这种特性可以实现光开关。     

Experimental study on polarization holographic storage in genetic mutant BR-D96N film

The information storage is developing toward high speed access and massive stor-age capacity. Optical holographic storage has not only high speed parallel data access and high addressing speed without mechanical motion but also high storage density with multiplexed volume holographic storage[1]. In recent years, optical holographic storage is studied intensely in the field of information storage. It has been shown that the polari-zation of light could also be recorded with polarization hologra…     

Polarization holographic gratings with high diffraction efficiency recorded in azopolymer PAZO

Azopolymers are one of the most efficient materials able to record the polarization state of light. They have numerous applications, such as data storage and diffractive optical elements with unique polarization properties. An essential parameter for each diffractive element is its diffraction efficiency η. In order to optimize the recording conditions and obtain high-efficient polarization holographic gratings, in the present work we study the dependence of the diffraction efficiency on the recording angle and thickness of a series of azopolymer layers. Three recording angles are used ??10°, 20° and 30° and three series of thin films with thicknesses 470, 850 and 2400 nm from the water-soluble azopolymer PAZO. The gratings are inscribed by two plain waves with left and right circular polarization from a He-Cd gas laser (442 nm). The diffraction efficiency of the gratings is probed with a right hand circularly polarized beam from a probe laser with wavelength 635 nm. The kinetics of diffraction efficiency η(t) in the +?1 diffraction order are presented and compared. Our experimental results indicate that highest diffraction efficiency (more than 40%) is obtained for the sample with thickness 2400 nm and for recording angle 10°. As the holographic recording in azopolymers is usually accompanied by formation of surface relief gratings, the surface topography of the recorded samples is also investigated by atomic force microscopy.     

BR-D96N薄膜共线全息图像存储实验研究

摘要:     利用一种生物光致变色材料—基因突变菌紫质BR-D96N薄膜的光致变色特性,实现了可擦写式共线全息图像存储实验.对于光密度为3.0的BR-D96N薄膜,在700 mW/cm2的记录光强下（波长为632.8 nm,物光、参考光光强比为约1:1.2）,全息图建立的最佳曝光时间约为3s,最佳再现光强约为50 mW/cm2,全息图寿命约为10 min.实验表明：共线全息存储技术光学系统简单,系统体积小,受存储环境的影响低,并能够实现高密度存储|同时也实验验证了BR-D96N薄膜具有响应速度快,感光灵敏度高,擦写次数高,稳定耐用,使用方便等优点,可以作为一种较灵敏的可擦写共线全息记录介质.     

Holographic recording and retrieval of polarized light by use of polyester containing cyanoazobenzene units in the side chain

We examined the holographic recording properties of polyester containing cyanoazobenzene units in the side chain. It was revealed that, when a linearly polarized object beam with an arbitrary polarization direction was recorded, the retrieved beam had the same polarization state as that of the object beam, with a constant diffraction efficiency of 0.1. Moreover, two object beams with mutually orthogonal linear polarization could be recorded and retrieved separately from the same area. This is, to our knowledge, the first example of holographic polarization multiplexing. The retrieved images were found to resolve details of ~40line pairs/mm and a 40-mum -pitched checkerboard pattern. The resolution of the system is limited by the CCD cameras that are used. Polarization encoding to increase the storage capacity and (or) the signal-to-noise ratio of holographic data recording is also discussed.     

Large inverse relaxation of photoinduced birefringence in an azobenzene-containing ionic self-assembly complex

Photoinduced anisotropy and polarization holographic recording were investigated in an azobenzene-containing ionic self-assembly complex. The complex film was found to possess large photoinduced dichroism (D～0.36) and photoinduced birefringence (Δn～10^?2). A noteworthy observation was that the photoinduced birefringence did not show any decay, but strongly increased after switching off the pump light at room temperature. The diffracted signals of the polarization holographic gratings, written by two orthogonally linear and circular polarized beams respectively, exhibited similar inverse relaxation behavior as the photoinduced birefringence after switching off the writing lights. A discussion about the mechanism accounting for the abnormal relaxation process of photoinduced birefringence is presented.     

Holographic grating recorded by He–Ne laser operating at 632.8 nm in polymer film containing push–pull azo dye

Holographic gratings were optically recorded by two beams from a He–Ne laser operating at 632.8 nm in poly (methyl methacrylate) (PMMA) film containing push–pull azo dye. The holographic characteristics of the recorded gratings were dependent on the polarization direction of the recording beams and the relationship between the diffractive signals and the power density of recording beams was investigated. The formation of holographic gratings accompanied by 532 nm (double-frequency of Nd:YAG laser) irradiation was studied in detail. It was found that the effect of 532 nm laser to the holographic grating lay in two aspects. The acceleration effect of 532 nm laser to the formation of holographic grating is predominant when the power density of 532 nm laser is low. While at relatively high power density of 532 nm laser, the erasure is the main factor to the holographic grating. Moreover, the holographic grating was probed by 532 nm laser at low power density and the dependence of the first order diffractive signal on the recording beam power density was also presented.     

Polarization holographic gratings in an azobenzene side-chain liquid-crystalline polymer

Polarization holographic recording was investigated in a liquid-crystalline azobenzene side-chain polymer. A highly stable polarization holographic grating with the diffraction efficiency of 12.6% was written in the polymer film by two orthogonally linearly polarized 532 nm beams with equal intensities of 150 mW/cm². The polarization grating was studied with a 633 nm probe beam by surveying the conversion of the polarization state of the probe beam and measuring the dependence of diffraction efficiency on the polarization direction of the probe beam. It was found that the ± first-order diffraction efficiency and the polarization of the diffracted wave depended strongly on the polarization of the readout wave. The unusual diffraction properties of the recorded grating were attributed to the presence of the circular photoinduced birefringence. PACS 42.40.Ht; 42.40.Lx; 78.20.Fm     

Saturation effect in azobenzene polymers used for polarization holography

The saturation behavior of diffraction efficiency has been experimentally studied and theoretically modeled in azobenzene polyesters by recording polarization gratings with two beams of orthogonal circular polarization. The model is an extension of the phenomenological expression of Kakichashvili, derived from the rate equations for photoanisotropic materials, taking into account the effect of saturation with time and intensity. The saturation model of the polyester material can be used for the computer simulation of a polarization holographic data storage system under development. The simulation is based on fast Fourier transforms, taking the parameters of the recording material and the optical processes into account. Agreement between measured and simulated results proves the applicability of the saturation model as an efficient tool in the optimization of the system. Received: 16 September 2002 / Published online: 3 April 2003 RID="*" ID="*"Corresponding author. Fax: +36-1/463-4194, E-mail: pvarhe@math.bme.hu     

Formation of positive and negative anisotropic holographic gratings depending on recording energy in photoreactive liquid crystalline copolymer films

Anisotropic diffractive gratings formed by birefringent molecular alignment are fabricated by a holographic technique using a photo-cross-linkable liquid crystalline copolymer (PLCCP). Depending on the exposure energy used for holographic recording, bright or dark regions of the interference fringe can be chosen for the molecular-aligned region, analogous to positive- and negative-type photoresist processing in photolithography. In conjunction with simultaneously generated surface relief gratings, the anisotropic refractive index modulation inherent in the PLCCP film exhibits different diffraction properties depending on the incident beam polarization. The anisotropic refractive index grating profiles are quantitatively presented for two cases determined by the exposure energy, based on the Fourier analysis of diffractive optics. The selection of different grating formations selected by varying only the exposure energy could provide a strategy for the fabrication of functionalized diffractive optical elements.