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Sub-picosecond region two dimensional parallel information processing in photorefractive crystals

光折变晶体中的亚皮秒区二维并行信息处理

基本信息

批准号：
05452108
负责人：
KURODA Kazuo
金额：
$ 4.48万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

We planned and carried out the following experiments : the pico-and subpico-second light pulses which bear the spatio-temporal information are recorded in and read out from volume holograms into which the temporal evolution is mapped spatially. For this aim, we developed the method to read out recorded gratings inside the volume hologram directly by measuring the diffraction efficiency and phase of cw laser beam as a function of angle detuning from the Bragg condition. The grating envelope function is obtained by solving the coupled mode equations inside the volume hologram. Then we recorded the interference fringes between the signal and reference beams, from the 3.5-picosecond duration mode-locked frequency-doubled Nd : YAG laster, inside a photorefractive LiNbO_3 crystal and could read out the information successfully.We measure the photorefractive sensitivities and time constants of LiNbO_3 and BaTiO_3 crystal for ultrashort pulses. We found that their responses strongly depended on the peak intensity of pulse, but they were independent of the pulse width. Especially, the sensitivity of LiNbO_3 increases an order of magnitude for intense input beams of several tens MW/cm^2. It is due to the intensity dependence of the photovoltaic effect. We also investigated the photorefractive effect of semi-insulating semiconductor GaP,and we obtained the information about its electrical state structure.

我们计划并进行了以下实验：将具有时空信息的皮秒和亚皮秒光脉冲记录到体全息图中，并从体全息图中读出，将时间演化映射到空间上。为了这个目的，我们开发了一种方法来读出记录的光栅内的体全息图直接通过测量连续激光束的衍射效率和相位作为一个函数的角度失谐从布拉格条件。通过求解体全息图内部的耦合模方程，得到了光栅包络函数。在此基础上，利用3.5皮秒锁模倍频Nd：YAG激光器，在光折变LiNbO_3晶体中记录了信号光和参考光的干涉条纹，并成功地读出了信息，测量了LiNbO_3和BaTiO_3晶体对超短脉冲的光折变灵敏度和时间常数。我们发现它们的响应强烈地依赖于脉冲的峰值强度，而与脉冲宽度无关。特别是对于几十MW/cm ^2的强流输入光束，LiNbO_3的灵敏度提高了一个数量级。这是由于光伏效应的强度依赖性。我们还研究了半绝缘半导体GaP的光折变效应，得到了它的电态结构信息。