Fabrication and characterization of poly(methyl methacrylate) photopolymer doped with 9,10-phenanthrenequinone (PQ) based derivatives for volume holographic data storage

We present our studies on the photopolymer of poly(methyl methacrylate) (PMMA) doped with 9,10-phenanthrenequinone based derivatives for volume holographic storage. By introducing different functional groups on the side-chain of 9,10-phenanthrenequinone molecule, the holographic characteristics of the material can be modified. The photoreaction involved with the holographic recording in the samples was investigated by measuring UV-Vis absorption spectrum and mass spectrum. The experimental results show that the similar behaviors were exhibited in these photopolymers. It is found that phase hologram recording in our PQ derivatives doped PMMA photopolymer involves a structure change of the quinone based molecule, which induces a strong change of the refractive index. Experimental characterizations on holographic data storage, including material sensitivity, dynamic range (M#) and bit-error-rate have been performed. We found that, by selecting appropriate functional groups, an improvement in sensitivity and M# for holographic data storage can be achieved.     

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.     

曙红敏化重铬酸盐明胶光声光谱的研究

用曙红敏化重铬酸盐明胶全息记录材料，用光声光谱技术测定了这种材料的光能吸收光谱，实验的结果表明，曙红是一种新的有价值的重铬酸盐明胶光谱增感染料，可以在５１４．５ｎｍ处形成强吸收峰，这对于记录彩色全息图和制作全息光学元件是有利的，光声光谱技术在全息记录材料的光谱增感与光化学过程的测量中，是一种极其灵敏又十分有效的方法。     

记录方式对光致聚合物中全息光栅形成过程的影响

根据光致聚合物记录机理,研究了不同记录方式对光栅衍射效率的影响.对已有的光致聚合物光栅形成的一阶扩散模型进行简化,求解出全息曝光、暗增长、均匀后曝光过程对应的折射率调制度的解析式.应用所得解析结果,对三种记录方式在不同光强下的折射率调制度动态进行数值模拟.采用蓝敏光致聚合物,分别在4 mW/cm~2和2 mW/cm~2光强下应用不同方式记录光栅,结果表明:如果曝光光强较高,暗增长的记录方式将获得相对高的饱和折射率调制度,而均匀后曝光会加速达到饱和的进程.     

Holographic polymer materials with diffusion development: Principles, arrangement, investigation, and applications

We present a review of information that has been published in the scientific literature on the mechanism of formation (development, enhancement) of holograms at the expense of the photochemical attachment of phenanthrenequinone molecules and other compounds to polymer chains and diffusion mixing of unreacted molecules, on different types of light-sensitive materials that realize this mechanism, on the application of these materials to create volume holographic elements, on recording of information, and for research purposes.     

Photopolymers — Holographic investigations,mechanism of recording and applications

The holographic characteristics of a broad class of photopolymerization systems of the acryl type — metal (Ba, Pb, Ca, Sr) acrylates and acrylamide — are investigated. The conditions — composition, recording light intensity and spatial frequency — for self-fixing real-time recording are defined. Holographic techniques are employed to determine some basic characteristics of the photopolymerization reactions — order of the photochemical reaction and diffusion coefficients of the monomers used. Experiments are carried out proving the suitability of the investigated photopolymerization systems for optical correlation processing.     

Enhancement of photochemical response in bulk poly(methyl methacrylate) photopolymer dispersed organometallic compound

The enhancement of photochemical response is investigated in Zinc methylacrylate organometallic compound and phenathrenequinone doped poly(methyl methacrylate) photopolymer experimentally and theoretically. In experiments, the improvement in photosensitivity due to ZnMA compound is presented quantitatively. The dynamics parameters, quantum yield and initiation rate of PQ molecules, are determined by nonlinear fitting the experimental curves. The theoretical model with nonlocal effect is proposed to explain the contribution of actual chemical process to the enhancement of photochemical response. The comparison of theoretical and experimental results is finally described. Two significant roles of ZnMA compound, as a catalyst to accelerate the photochemical reaction and as a reactant to participate in the photoattachment with PQ molecules, are demonstrated quantitatively. The time constant of grating formation 20.9 s and the photosensitivity 2.3×10⁻⁵ cm²/J are experimentally obtained in an optimized 0.1 wt% ZnMA doped PQ-PMMA sample. This study contributes the physical mechanism for improvement of photosensitivity and provides significant theoretical foundation for advance the properties of materials in holographic memory.     

Influence of Post－baking and Delaying Processes on Dichromated Holograms：Their Mechanism

ＩｎｆｌｕｅｎｃｅｏｆＰｏｓｔ－ｂａｋｉｎｇａｎｄＤｅｌａｙｉｎｇＰｒｏｃｅｓｓｅｓｏｎＤｉｃｈｒｏｍａｔｅｄＨｏｌｏｇｒａｍｓ：ＴｈｅｉｒＭｅｃｈａｎｉｓｍＷＡＮＧＧｕｏｐｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓ，ＷｕｈａｎＵｎｉｖｅｒｓｉｔ...     

Dynamic phase holograms in anthracene-containing polymer layers under conditions of rapid diffusion

A model of the dynamics of phase holographic gratings in a polymer layer containing monosubstituted anthracene and a solvent-plasticizer is developed for the case when diffusion of all low-molecular components occurs. Good agreement between this model and the experimental data is demonstrated. It is shown that the photoinduced trapping and diffusion of solvent molecules also occur in highly plasticized polymer matrices, affecting significantly the dynamics of holographic gratings. Differences in the dynamics of holograms under conditions of rapid diffusion and thermolysis of the photoproduct (the photodimer) are noted. The trends in variations of the recording parameters as a function of the solvent content are revealed.     

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     

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.     

Liquid crystals in dynamic holography (review)

We review basic schemes and methods of recording of holographic gratings in liquid crystals, compositions, and devices on their basis. We consider various photochemical and electrooptical mechanisms of this recording, as well as some particular applications of dynamic holography in liquid crystals.     

Photochemically deposited surface relief gratings of an azo-dye-labeled phospholipid from the aqueous phase

Surface relief holographic gratings are fabricated on the polybutadiene-coated walls of a cell filled with an aqueous solution of an azo-dye-labeled phospholipid. A low power (2 mW) 488 nm argon ion laser wavelength is used. Laser-excited azo dye reacts to produce a permanent surface-relief pattern on the polybutadiene substrate. Gratings are recorded for varying concentrations of the phospholipid solution as well as laser intensity. Lithographic masks are used to show that the photochemical pattern on the substrate is an exact replica of the light intensity distribution, and so the technique can be used for holographic recording as well as for biomolecular applications.     

一种微光刻全息记录新材料：光刻蚀纤维素软片成像机理及其特性研究

报道一种新型的聚合物全息记录材料：光刻蚀纤维素软片（ＰＣＦ），对该材料较强的实时特性、较高的分辨本领、线性的表面浮雕调制特性等进行了实验研究，同时通过电子自旋共振谱（ＥＳＲ）、红外谱（ＩＲ）等手段研究了其成像过程中的光化学反应过程，证实了它的光降解机理。     

Pyroelectric drive for light-induced charge transport in the photorefractive process

We calculate the influence of thermal patterns and pyroelectric fields on photorefractive holographic recording in terms of a one center charge transport model, taking into account diffusion, photovoltaic current and space charge limitation. At pulse laser intensities the pyroelectric effect can enhance the holographic sensitivity and the saturation value of refractive index changes significantly.     

Nonstationary amplification of holographic gratings in birefringent photorefractive crystals

A theoretical model of nonstationary self-amplification of weak holographic gratings in birefringent photorefractive crystals with two-and one-frequency readout is presented. The model takes account of the multiwave and vector character of the interactions and the simultaneous occurrence of intra-and intermode recording and diffraction processes with different phase detunings and complex coupling constants, which take account of the local and nonlocal response mechanisms of the medium. Analytical solutions are obtained for the intercoupled recording and diffraction equations. The results of numerical calculations of the kinetics of the spatial amplitude-phase profile and gain of the holographic grating and the selective amplification properties with intra-and intermode interaction geometries are presented. Zh. Tekh. Fiz. 67, 68–77 (April 1997)     

Imaging properties of a 2D crossed holographic grating on silver halide photoemulsions

A technique is proposed for photochemical processing of photoemulsions, which makes it possible to form lens-shaped focusing elements at the nodes of crossed 2D holographic gratings (2DHGs). The results of experiments on 2DHG recording performed on PFG-01 material using this technique show considerable improvement of imaging properties of 2DHG.     

Highly concentrated phenanthrenequinone-doped poly (MMA-co-ACMO) for volume holography

Novel composite materials are synthesized by incorporating N-acryloylmorpholine(ACMO) in highly concentrated phenanthrenequinone(PQ) doped poly(methyl methacrylate)(PMMA). The photosensitizer concentration of PQ was increased from 0.7 wt. % to 1.8 wt. %. The doping of ACMO component results in a higher diffraction efficiency and photosensitivity than a typical PQ/PMMA system. The enhanced performance of the material may stem from the ACMO molecules, which might open a new route for improving the holographic performance of the PQ/PMMA photopolymer.     

Single-layered light-emitting diodes possessing methoxy-modified pyrazoloquinoline dyes in poly-N-vinylcarbazole matrix

A principal opportunity to operate by current-voltage and electroluminescent-current dependences for the single-layered light-emitting diodes (LED) on the basis of the polyvinylcarbazole (PVK) polymers doped by methoxy-substituted pyrazoloquinoline (PQ) emitting dye chromphore is demonstrated. The principal light-emitting parameters in the architecture ITO/PQ: PVK/Ca (Al) were investigated. The maximally achieved quantum efficiency of the investigated LED was equal to about 0.87% and corresponded to the brightness about the 44 Cd/m². The absence of blue shift for the electroluminescence (EL) compared to PL may indicate on an absence of near-the-surface exciton diffusion for the methoxy-PQ contrary to the phenyl-methyl-substituted PQ. The quantum chemical calculations have shown principal role of the dye chromophore state dipole moments in the observed carrier kinetics determining the EL.     

Formation of Holographic Transmission Diffraction Gratings in Absorbing Photopolymer Media

The formation of holographic transmission gratings in absorbent photopolymer materials (PPM) is studied theoretically. Analytical model describing a spatiotemporal transformation of holographic grating field during record is developed with allowance for optical absorption and diffusion processes. It is demonstrated that optical attenuation during record causes the spatial inhomogeneity of refractive index grating profile and of the its growth kinetics. A degree of influence of optical attenuation on the integral diffraction characteristics is evaluated based on numerical simulation. The kinetics of record of high-efficient transmission holograms in PPM is experimentally investigated. Based on a comparison of theoretical and experimental time dependences of diffraction efficiency, physical parameters of the examined PPM are determined and adequacy and tendency in the development of the suggested mathematical model are evaluated.