Manganese-doped YAIO/sub 3/: A potential material for holographic recording and data storage

We report, we believe for the first time, the experimental observation and study of lightinduced surface holographic gratings that are due to the direct photoexpansion ofAs,S, ChG thin films. Our ChG samples are fabricated by thermal vaporization. They are well adapted for waveguiding applications in the infrared band, having high optical quality and thickness (d)varyingfromd= 1.1 tod=2.5km.Forthe holographic recording, the 488 nm line of a cw argon laser is used as the excitation wavelength. This wavelength is near the bandgap (hg = 527 nm or E, 2.35 eV) for our ChG films. The total power ofthe two writing beams is 21 mW on an illumination surface of 4 X 4.5 mm2. The study of exposed ChG film surface demonstrates clear relief modulation gratings via photoexpansion. The photomodulation of the thin ChG film's thickness does not require additional processing, thus is real time and self developing. The growth of relief gratings amplitude is almost the same for used SiO, and oxidized silicon wafer substrates (Fig. 1). The further dynamics of surface modulation are not monotone, which is similar to the typical kinetics of holographic diffraction efficiency detected earlier in ChG materials. This and some other experimental data indicate a possible significant role of surface gratings in the holographic efficiency. The recorded relief gratings are stable and show large memory effect of at least several months (Fig. 2). Heating of the sample above T = 140 OC (the glass transition temperature is Tg = 180 "C) erases efficiently the relief modulation. Observations through an optical microscope clearly show, in addition to the relief modulation, the existence of regular dark and transparent regions result-