Photochemical kinetics for holographic grating formation in phenanthrenequinone doped poly (methyl methacrylate) photopolymer

The photochemical kinetics of phenanthrenequinone (PQ) doped poly (methyl methacrylate) photopolymer in holographic recording was studied theoretically and experimentally. The diffusion of PQ molecules during holographic recording was negligible because of its small diffusion coefficient at room temperature. A photochemical reaction kinetics model of PQ/PMMA was established. The analytical expressions for the temporal variations of transmittance and diffraction efficiency were derived. By fitting the experimental curves, some parameters related with the polymer components were obtained by the proposed model, which can be used to analyze the photochemical process and will be helpful to the optimization of material preparation.     

Analysis of temperature change effects on hologram recordingand a compensation method

For commercialization of holographic storage drives, the effects of temperature changes on holographic medium is critical. There has been no systematic study on the effect of temperature change on hologram recording properties. We believe that the monomer-diffusion speed and polymerization rate changes are critical for hologram-recording properties and estimate those parameters on each temperature using the photopolymer medium process simulation we have developed. We describe how these parameters affect actual recording properties such as sensitivity, M=# and so on. Moreover, we propose a method for compensating temperature changes, and confirm the success of this.     

Study of holographic characteristics of photopolymers with two photoinitiator systems

The acrylamide-based photopolymer, one kind of holographic storage material that contains the photoinitiation triethanolamine and N-phenylglycine, was prepared and compared with the photopolymer material containing one photoinitiator. The results indicate that this material shows attractive recording characteristics, which include diffraction efficiency, refractive index modulation, sensitivity and so on. Temporal changes in transmission efficiency with various incident intensities are studied; the angular width of the photopolymer material is also measured.     

Real-time measurement of photo-induced effects in 9,10-phenanthrenequinone-doped poly(methyl methacrylate) photopolymer by phase-modulated ellipsometry

The photo-induced effects in 9,10-phenanthrenequinone-doped (PQ-doped) poly(methyl methacrylate) (PMMA) photopolymer were studied by phase-modulated ellipsometry and polarimetry in real time. The PQ-doped PMMA was exposed to an Ar/Kr tunable laser at the wavelength of 488 nm and measured by a HeNe laser (632.8 nm). We measured the induced birefringence and the variation of the refractive index separately during exposure; there was a difference of three orders of magnitude between these two effects. This suggested that the physical mechanism of holographic recording in PQ-doped PMMA is mainly due to the photo-induced variation in the refractive index.     

碱性品红敏化的光致聚合物在441nm短波长的全息存储特性研究

制备了一种以碱性品红为光敏剂的新型全息存储材料,且使用波长为441nm的He—Cd激光器成功研究了材料的全息特性。研究表明,该材料在短波长处仍具有较高的衍射效率、曝光灵敏度和较大的折射率调制度,衍射效率近60％,灵敏度为2．93×101c群／mJ,折射率调制度为8．85×10．。。在存储介质膜中存储了全息图像,再现图像较为清晰,对比度与保真度较为理想,说明该材料具有较好的全息存储性能,适合作为高密度全息存储介质。     

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.     

番红花红T光敏感光致聚合物全息存储材料

制备了一种以番红花红T为光敏剂的新型全息存储材料,主要用Ar⁺激光器的514.5nm波长的绿光研究材料的全息特性.研究表明,该材料具有较高的衍射效率、曝光灵敏度和较大的折射率调制度,衍射效率近40%,灵敏度为7.22×10^-4cm²/mJ,折射率调制度为3.65×10^-4,同时,在读出时必须考虑布拉格偏移对全息存储的影响.在介质膜中存储了全息图像,再现图像较为清晰,说明该材料适合用作高密度全息存储介质. 关键词： 全息存储 光致聚合物 衍射效率 布拉格偏移     

偶氮苯衍生物的全息光存储和双折射特性研究

对6-（4-（（4-（十八烷氧基-）苯基）二氮烯基）苯氧基）-1-己醇（E-1-ol）的光致变色、双折射和全息光存储特性进行了研究.以488 nm的氩离子（Ar+）激光为抽运光,632.8 nm 的氦氖（He-Ne）激光为探测光,研究了透射信号强度随时间的变化关系;在10 mW~160 mW的范围内,研究了透射信号强度的最大值随抽运光功率的变化;经计算,在各抽运光功率下,获得的光致双折射值（δn）达10－2量级,最大激光功率下,获得的δn为2.8×10－2.对透射信号强度随时间的变化曲线进行了理论拟合,得出曲线的上升和下降符合双指数增长和衰减,时间响应常量分别是：上升阶段：t1=4.8 s,t2=85.8 s;下降阶段：t1=1.9 s,t2=27.6 s.用等强度s偏振的两束Ar+激光为写入光, He-Ne光为读出光,研究了衍射信号强度随时间的变化及写入光功率改变时,衍射信号强度最大值与写入光功率的变化关系;对衍射信号强度随时间变化的动力学过程进行了理论拟合,得出光栅生长和衰减也有快和慢两个过程,光栅生长时间响应常量为：t1=3.9 s,t2=33.9 s,光栅衰减时间响应常量为 t1=1.8 s,t2=60.1 s.     

A wideband sensitive holographic photopolymer

A novel wideband sensitive dry holographic photopolymer sensitized by rose bengal (RB) and methylene blue (MB) is fabricated, the holographic storage characteristics of which are investigated under different exposure wavelengths. The result shows that the sensitive spectral band exceeds 200 nm in visible light range, the maximum diffraction efficiency under different exposure wavelengths is more than 40% and decreases with the decrease of exposure wavelength, the exposure sensitivity is not change with the exposure wavelength.This photopolymer is appropriate for wavelength multiplexing or multi-wavelength recording in digital holographic storage.     

Two-photon recording of microholograms in photopolymer materials with new cationic thioxanthone photoinitiators

We have demonstrated two-photon induced recording of the microholograms at an arbitrary point within thick (∼100 μm) photopolymer material using photoinitiators on a basis of new cationic thioxanthone derivatives. Such material provides high values of refractive index change Δn = 4.8 × 10⁻³, and holographic recording sensitivity S = 1.2 cm/J. A nanosecond laser pulse at a wavelength of 532 nm was used for recording. For the selective on the depth reading of the microholograms the method of collinear heterodyning was applied.     

非水溶性红敏光致聚合物全息性能的改善及其应用研究

为使非水溶性红敏光致聚合物材料的全息性能得到改善,采用复合光敏增感、复合引发和复合单体的方法反复对比实验,改善后体系的灵敏度为0.02 cm2/mJ,衍射效率高达83%,计算得到材料的最大折射率调制度为4.1×10-3.实验结果和理论分析表明,利用该材料制作的新型全息光栅具有损耗低、通道宽度窄、衍射效率高等优点,适于制作光通信中的波分复用器及各种光学元件.     

Experimental study of multiplexed holographic gratings recorded in a photopolymerizable silica glass

Recently the capability of photopolymerizable sol–gel materials to angular multiplex holographic gratings has been demonstrated [1, 2]. In this study, holographic transmission gratings were recorded using angular multiplexing in a silica glass doped photopolymer holographic recording material. The time interval between exposures and the angular selectivity were analyzed, in particular their effects on the dynamic range. By using the optimal parameters gratings of similar response were achieved with values of M/#=4.8, as well as good values of diffraction efficiency with high photosensitivity. PACS 42.40.Pa; 42.70.Ln     

新型双染料敏化的宽带光聚物全息特性研究

报道了一种新型、两种染料共同敏化的宽带响应光聚物材料.该材料使用孟加拉玫瑰红和亚甲基蓝作为联合光敏剂,由于混合染料的加入,使材料的感光光谱范围大大加宽.用四种波长的光对样品进行曝光,衍射效率均大于40%,最高可达80%,适合于多波长存储,分别用不同波长的激光在样品同一位置存储了四幅不同的图像,其再现图像效果良好,表明该材料是一种较理想的多波长全息存储材料.     

Evaluation of polycarbonate substrate hologram recording medium regarding implication of birefringence and thermal expansion

In this paper, we evaluate photopolymer media using a polycarbonate (PC) substrate. In holographic data storage medium, substrates that sandwich the photopolymer material are needed to protect the photopolymer material against exogenous shock and open air. An optical glass such as BK-7 is normally used as a substrate, but a PC substrate has a cost advantage and is easy to fabricate compared with optical glass. For holographic recording and reading, however, the high birefringence and high thermal expansion of a PC substrate are significant problems. First, we analyze the degree of degradation of output power by the polarization change and estimate the threshold value of birefringence to record hologram normally. Next, we estimate the temperature tolerance of hologram readout with polycarbonate substrate hologram medium. These analyses results indicate the possible usage of the PC substrate as holographic recording media.     

Characterization of phenanthrenequinone-doped poly(methyl methacrylate) for holographic memory

The holographic recording characteristics of phenanthrenequinone- (PQ-) doped poly(methyl methacrylate) are investigated. The exposure sensitivity is characterized for single-hologram recording, and the M/# is measured for samples as thick as 3 mm. Optically induced birefringence is observed in this material.     

Optimization of a 1 mm thick PVA/acrylamide recording material to obtain holographic memories: method of preparation and holographic properties

Information holographic storage is a very promising technique due to its high theoretical capacity. One of the key factors in developing holographic memories is the need for a suitable recording material which must have certain specific characteristics. In particular, in order to achieve a high storage density it is necessary to work with great thicknesses. One of the essential requirements for holographic memories to be competitive is that the material must have a thickness of 500 μm or more, but it is not easy to find such thicknesses with the photopolymers currently available. In this study, we develop a method of preparing layers of a polyvinyl alcohol/acrylamide based photopolymer approximately 1 mm thick. Optimization of this material makes it possible to obtain good results for the main holographic parameters; diffraction efficiency 70% and energetic sensitivity 50 mJ/cm². PACS 42.70.Ln; 42.40.Pa; 42.40.Ht An erratum to this article can be found at .     

番红花红T敏化的新型光致聚合物全息存储材料

制备了一种以番红花红T为光敏剂的新型全息存储材料,实验结果表明,该材料具有较高的衍射效率、曝光灵敏度和较大的折射率调制度等,最大衍射效率约38.5%,折射率调制度为0.547×10－3,在存储介质膜中存储了模拟全息图像,再现图像有较好的保真度,说明该材料适合用作高密度体全息存储介质。     

双波长敏感的非水溶性光致聚合物存储特性研究

研究了一种新型的对红光和蓝光敏感的非水溶性光致聚合物材料的全息存储特性。该聚合材料由复合单体、复合光敏剂、复合引发剂、链转移剂及成膜物等成分组成,它具有防潮、后处理简单、分辨率高及耐高温等特点,对红、蓝光2种衍射效率均不低于75%,灵敏度为(45～65)mJ/cm2。对该材料先后进行了双波长复用存储实验和角度复用存储实验,当用红光或蓝光再现时再现图像清晰可见,相邻2副图像之间无明显干扰,说明该材料具有良好的存储性能,适合作高密度数字全息存储的记录材料,可用作光通信中的波分复用器及其他光学元件。     

Recording media that exhibit high dynamic range for digital holographic data storage

A general strategy for fabricating thick, optically flat photopolymer recording media with high dynamic range (M/#) that exhibit low levels of recording-induced Bragg detuning for holographic data storage is presented. In particular, media with M/# values as high as 42 in 1-mm-thick formats are obtained. We believe that these results are the first demonstration of a holographic storage medium with a dynamic range of this magnitude. In addition, we report the holographic recording and recovery of high-capacity (480-kbit) digital data pages in these media, further illustrating their data-storage capabilities.     

一种核黄素敏化的宽带全息记录材料

制备了一种核黄素敏化的以聚乙烯醇为基质的新型全息存储材料,并研究了材料的全息特性.用Ar+激光器激发的488 nm的蓝光对材料曝光,结果表明该材料具有较高的衍射效率和曝光灵敏度,衍射效率高达53%,灵敏度为3.3 cm2/J,折射率调制度为4.5×10－4.研究了材料的透过率与随时间和入射角度变化的关系,说明在曝光记录过程中有噪音光栅生成.在存储介质膜中存储了全息图像,再现图像较为清晰,说明该材料适合用作高密度全息存储介质.