PERSISTENT HOLE-BURNING IN FINE PARTICLE SYSTEMS

点击翻译按钮获取中文摘要

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.