Holographic Grating Formation in Photochromic Diarylethene-Doped Polymeric Thin Films

We introduce a model to describe real-time grating formation in holographic photochromic diarylethene-doped polymeric thin films. This model, which combines photochromic chemical reaction with the coupled-wave theory,indicates that the grating recording time depends on the molecular absorption coefficient of molecules and the quantum yield of the photochromic reaction at a certain holographic recording intensity. The model is validated by comparing its predictions with the experimental results in which photochromic molecule 1,2-bis(2-methyl-5-(4-formylphenyl)-3-thienyl) perfluorocyclopentene doped PMMA films were used.     

Coherence preservation during light-surface plasmon polaritons-light transformation

We constructed a four-layer system composed of a prism,a silver film,an air layer and a lithium niobate crystal.Initially we used two coherent light beams to excite surface plasmons.The surface plasmons were then decoupled into light in the photorefractive crystal where a holographic grating was recorded.The two beams remained coherent through light to surface plasmons to light transformation.Studying the characteristics of the holographic grating we found out that the thickness of the grating was to the order of hundreds of microns.The thick holographic grating suggests that the holographic recording in the photorefractive materials was induced by the leaky waves rather than by surface plasmon polaritons directly.     

Dynamic analysis of holographic gratings in amulti-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.     

Land/groove optical recording with GeTe/Sb2Te3 superlattice-like structure

A superlattice-like (SLL) structure was applied to phase-change optical recording. The recording layer consisting of alternating thin layers of two different phase-change materials, GeTe and Sb2Te3, were grown by magnetron sputtering on polycarbonate substrates. Land/groove optical recording was adopted to suppress crosstalk and obtain a large track density. Dynamic properties of the SLL disc were investigated with the shortest 1T pulse duration of 8 ns. Clear eye pattern was observed after 10000 direct overwrite cycles. Erasability above 20 dB was achieved at a constant linear velocity of 19 m/s. Carrier-noise ratio (CNR) kept above 46 dB when the recording frequency reaches 21 VIHz. The SLL phase change optical disc demonstrates a better recording performance than the Ge1Sb2Te4 and Ge1Sb4Te7 discs in terms of CNR, erasability, and overwrite jitter.     

基于PPARα激动剂的融合药效团模型的构建及评价

Pharmacophore is a commonly used method for molecular simulation, including ligand-based pharmacophore (LBP) and structure-based pharmacophore (SBP). LBP can be utilized to identify active compounds usual with lower accuracy, and SBP is able to use for distinguishing active compounds from inactive compounds with frequently higher missing rates. Merged pharmacophore (MP) is presented to integrate advantages and avoid shortcomings of LBP and SBP. In this work, LBP and SBP models were constructed for the study of peroxisome proliferator receptor-alpha (PPARα) agonists. According to the comparison of the two types of pharmacophore models, mainly and secondarily pharmacological features were identified. The weight and tolerance values of these pharmacological features were adjusted to construct MP models by single-factor explorations and orthogonal experimental design based on SBP model. Then, the reliability and screening efficiency of the best MP model were validated by three databases. The best MP model was utilized to compute PPARα activity of compounds from traditional Chinese medicine. The screening efficiency of MP model outperformed individual LBP or SBP model for PPARα agonists, and was similar to combinatorial screening of LBP and SBP. However, MP model might have an advantage over the combination of LBP and SBP in evaluating the activity of compounds and avoiding the inconsistent prediction of LBP and SBP, which would be beneficial to guide drug design and optimization.     

Scattering Noise Properties of Holographic Photopolymers by Means of Real-Time Transmittance Analysis

We propose a simplified model to analyse the temporary behaviour of transmittance for holographic photopolyreefs, based on the existing first-harmonic diffusion theory, with assumptions of constant polymerization coefficient and negligible diffusion effect for noise gratings. By applying this model to measure real-fime transmittance of our novel blue-sensitized photopolymer, the bleaching time constant of dye and polymerization rate are extracted, and the effect of the material composite on the noise property is revealed. This provides a prompt method to assess the performances of holographic photopolymers.     

Force criterion of different electrolytes in microchannel

The control and handling of fluids is central to many applications of the lab-on-chip. This paper analyzes the basic theory of manipulating different electrolytes and finds the two-dimensional model. Coulomb force and dielectric force belonging to the body force of different electrolytes in the microchannel were analyzed. The force criterion at the interface was concluded, and testified by the specific example. Three basic equations were analyzed and applied to simulate the phenomenon. The force criterion was proved to be correct based on the simulation results.     

Fabricating blazing grating on NGD by photochemical etching

This paper tries to introduce the reader to the method of using photochemical re-action to copy holographic optical elements(HOEs)in relief.The holographic blazing gratingso copied is groove depth adjustable phase modulability enlarged through copying and 3.3times the diffraction efficiency(DE)of the original grating.It is expected that the newmethod will lead to the mass production of the light-weight HOEs at low cost.     

Role of Ag microalloying on glass forming ability and crystallization kinetics of ZrCoAgAlNi amorphous alloy

Bulk metallic glasses(BMGs) with new chemical compositions(ZrCoAgAlNi) were fabricated and the effects of Ag minor addition on the glass forming ability(GFA) and crystallization kinetics were studied. The x-ray diffraction(XRD) test was applied to identify the amorphousness of BMGs or possible crystalline phases. Using differential scanning calorimeter(DSC), the thermal stability and crystallization kinetics under a non-isothermal condition at the different heating rates were studied. Considering the heating rate dependency of glass transition and crystallization kinetics, the activation energy was evaluated and measured for the mentioned processes. It was revealed that the rise in Ag content led to the decrease in activation energy for glass transition, while the activation energy for crystallization increased. The thermal stability and GFA were also studied and it was found that the Ag addition strongly affected the inherent features of BMGs. With the increase in Ag content, the atomic mobility and structural rearrangement changed in the material and consequently, the GFA and thermal stability were significantly improved.     

Investigation on the phase shifts of extinction and phase gratings in polymethyl methacrylate

The phase shifts of the extinction and refractive index gratings to the illumination pattern are revealed in doped polymethyl methacrylate （PMMA）. The dynamic process of these shifts is studied via two-wave coupling at 351 nm. It is shown that these shifts are from the strain and the shrinkage inside the sample and accompanied with the photo-repolymerization process during the building process of the holographic grating. Such shifts will cause obvious energy exchange between the two recording beams and enough attention should be paid to the nonlocal property of the holographic gratings of the material in the application.     

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