Abstract

The dynamics of photoinduced absorption and holographic-grating recording in photorefractive crystals of bismuth silicate is studied. It is shown that, with the use of nanosecond laser pulses and of the intensity on the order of 1 MW/cm² or higher, the induced absorption due to population of the short-lived trapping levels, with characteristic relaxation times about several milliseconds or tens of milliseconds, is the case. Recording of dynamic holograms has been realized in these conditions in bismuth silicate crystals. Two mechanisms of holographic-grating recording, with the lifetimes differing by three orders of magnitude, are established. At relatively low intensities, about 1 MW/cm² or lower, the medium response is determined by a photorefractive mechanism of nonlinearity, with relaxation times of several seconds. At the intensities exceeding 5 MW/cm², one can observe a fast (ms relaxation times) component that may be associated with population of the short-lived traps. It is shown that the contribution of each mechanism is greatly dependent on the intensity of laser radiation and, for the intensities above 10–15 MW/cm², the short-lived traps having millisecond lifetimes play the decisive role.

中文翻译：

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硅酸铋晶体中动态全息图的光诱导吸收和脉冲记录

摘要

研究了硅酸铋光折变晶体中光诱导吸收和全息光栅记录的动力学。结果表明，通过使用纳秒级的激光脉冲和强度为1 MW / cm ²或更高的量级，归因于短期俘获能级的填充而引起的吸收，具有大约几毫秒或几毫秒的特征弛豫时间。就是几十毫秒。在这些条件下已经在硅酸铋晶体中实现了动态全息图的记录。建立了两种全息光栅记录机制，其寿命相差三个数量级。在相对较低的强度下，约为1 MW / cm ²小于或等于2时，介质响应由非线性的光折变机制确定，松弛时间为几秒钟。在强度超过5 MW / cm ^2时，可以观察到一个快速的（毫秒弛豫时间）分量，该分量可能与短寿命陷阱的数量有关。结果表明，每种机制的贡献在很大程度上取决于激光辐射的强度，对于强度在10-15 MW / cm ^{2以上的光}，具有毫秒寿命的短寿命陷阱起着决定性的作用。