PERSISTENT HOLE-BURNING IN FINE PARTICLE SYSTEMS

我们研究了ZnS：Sm纳米晶体中发现的新颖的光存储效应。它在外观上与持续光谱烧孔非常相似，但入射光的入射角和波长是记忆的。首先，我们澄清了这种效应是由多重散射光的干涉图样通过光漂白的记录引起的。因为这是一种空间烧孔效应，所以与温度无关，孔宽很窄。我们通过观察染料掺杂聚合物薄膜粉末中的相同效应证实了这一机制。对数据存储密度进行了估算，其数据存储密度约为目前使用的光盘的4 × 10_4倍。此外，通过加强样品的散射能力，我们发现了光子弱局域化的证据。还发现，燃烧光的偏振方向通过这种光学记忆效应而被记忆。研究了BaClF：Sm ~（2+）晶体的光致荧光强度的变化，发现在325 nm He-Cd激光激发下，Sm ~（2+）的荧光强度随时间的延长而减弱，而在488 nm Ar激光激发下，Sm ~（2+）的荧光强度随时间的延长而恢复。实验还发现，发光强度的变化与时间的对数成正比，其系数与激光强度和样品温度有关。这些结果表明，这种材料不仅满足表现出新颖的光存储效应的条件，而且使我们能够读出存储的数据，而没有大的干扰。此外，使用这种材料，可以多次重复地存储和擦除信息。这种记忆效应可能在高密度光学数据存储中找到实际应用。

We have investigated the novel optical memory effect that we discovered in ZnS : Sm nariocrystals. It is very similar to persistent spectral hole-burning in appearance, but the incident angle as well as the wavelength of the incoming light is memorized. First, we clarified that this effect arises from the registration of the interference pattern of the multiplescattered light through photo bleaching. Because this is a kind of spatial hole-burning effect, the hole-width is narrow irrespective of temperature. We confirmed this mechanism by observing the same effect in powders of dye-doped polymer film. The estimation of thedata storage density was attempted and it was shown to be as high as about 4 x 10_4 times of that in currently used compact disc. Further, by strengthening the scattering power of the sample, we found evidence of the weak localization of photons. It has also been found that the polarization direction of the burning light is memorized by this optical memory effect. Investigation of the photo induced variation of the fluorescence intensity in BaClF:Sm2+ crystals revealed that Sm2+ fluorescence decreases with time when the 325-nm He-Cd laser light is irradiated, while it recovers under the 488-nm Ar-laser light excitation. It was also found that the variation of the emission intensity is proportional to the logarithm of time, and its coefficient is dependent on the laser light intensify and sample temperature. These results indicate that this material not only satisfies the conditions for exhibiting the novel optical memory effect, but also enables us to read out the stored data without large disturbance. Further, using this material, it is possible to store and erase information many times repeatedly. This memory effect might find practical applications in high-density optical data storage.