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High-performance liquid crystals for next-generation in formation technologies

用于下一代形成技术的高性能液晶

基本信息

批准号：
13305063
负责人：
IKEDA Tomiki
金额：
$ 31.62万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

Holography, which enables optical storage of three-dimension images, has been of great interest for photonic applications. To obtain clear images, Bragg hologram that theoretically achieves 1O0-% diffraction efficiency is required. In the Bragg hologram, materials should be optically sensitive, meaning that refractive index is efficiently changed by light. Liquid crystals, showing large optical anisotropy and fluidity, can be a good candidate for holographic materials since a large change in refractive index can be easily induced by external fields. There is another important characteristic in the hologram : reversibility of recording. Commercially available materials are sensitive enough, while images cannot be erased, which limits the application to photonic devices. Azobenzene is one of the outstanding photochromic molecules that are capable of changing absorption, molecular shape, and refractive index reversibly upon photoirradiation. Consequently, polymer liquid crystals incorpora … More ted with an azobenzene moiety are naturally expected to be reversible holographic materials.In this study, two types of hologram, transmission-type and the Lippmann-type, were investigated using polymer azobenzene liquid crystal films. A linearly polarized beam from Ar^+ laser at 488 nm was split to two beams and interfered in the film with a crossing angle of 14゜ in transmission type and 180゜ in the Lippmann-type, respectively. Formation behavior of the transmission-type grating was probcd with a linearly polarized beam from He-Ne laser at 633 nm. The Lippmann-type grating was evaluated with transmission spectrum. In the transmission type, diffraction of the probe beam appeared upon irradiation of writing beams at 488 nm. Diffraction efficiency (η), that is defined as the ratio of diffraction intensity during irradiation to transmission intensity before irradiation, increased to 14% on photoirradiation. On the other hand, in the Lippman-type grating, the value of q for 500-nm light reached 43% when the film was irradiated at 350 mW/cm^2 for 60 min. Less

全息技术能够实现三维图像的光学存储，在光子应用方面引起了极大的兴趣。为了获得清晰的图像，理论上需要达到100%衍射效率的布拉格全息图。在布拉格全息图中，材料应该是光学敏感的，这意味着折射率被光有效地改变。液晶具有较大的光学各向异性和流动性，可以作为全息材料的一个很好的候选者，因为它的折射率很容易在外场的作用下发生大的变化。全息图还有一个重要的特性：记录的可逆性。商业上可用的材料足够敏感，而图像不能被擦除，这限制了光子器件的应用。偶氮苯是一种出色的光致变色分子，它在光照射下能够可逆地改变吸收、分子形状和折射率。因此，含有偶氮苯部分的聚合物液晶自然有望成为可逆全息材料。本研究利用聚合物偶氮苯液晶薄膜研究了透射型和李普曼型两种类型的全息图。将来自488 nm的Ar^+激光的线偏振光束分成两束，分别以14 lippmann -型和180 lippmann -型的交叉角干涉薄膜。利用633 nm的氦氖激光线偏振光束对透射型光栅的形成行为进行了研究。用透射谱法对lippmann型光栅进行了评价。在透射型中，探测光束在488nm处受到写入光束照射后出现衍射。衍射效率（η），即辐照时衍射强度与辐照前透射强度之比，在光能照射下提高到14%。另一方面，在lippman型光栅中，当薄膜以350 mW/cm^2照射60 min时，500 nm光的q值达到43%。少