Persistent refractive index gratings in bismuth germanium oxide doped with chromium

The kinetics of the production and dark-decay of index gratings in chromium-doped bismuth germanium oxide Bi12GeO20 (BGO) and undoped BGO were investigated as a function of temperature from room temperature to about 500 K. During the write process in undoped BGO the gratings show a fast leading edge peak, which drops quickly to a steady saturated value. The leading-edge peak does not change significantly at the higher temperatures. Grating production was much slower in the BGO:Cr samples and the gratings grew monotonically throughout the 0.5 s write interval. At room temperature the gratings in BGO:Cr are highly persistent. A grating written at room temperature retains 70% of its initial strength after 24 h when it was read only once an hour. Optical erasure plays a major role in the decay of such gratings; reading the grating every 6 min reduced its strength to 48% of its initial value after 24 h. The grating written at room temperature and monitored as the sample was heated decayed within the same 10 K ...