Persistent refractive index gratings in bismuth germanium oxide doped withchromium

The kinetics of the production and dark-decay of index gratings in chromium -doped bismuth germanium oxide Bi12GeO20 (BGO) and undoped BGO were investi gated as a function of temperature from room temperature to about 500 K. Du ring 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 pe ak does not change significantly at the higher temperatures. Grating produc tion was much slower in the BGO:Cr samples and the gratings grew monotonica lly throughout the 0.5 s write interval. At room temperature the gratings i n BGO:Cr are highly persistent. A grating written at room temperature retai ns 70% of its initial strength after 24 h when it was read only once an hou r. Optical erasure plays a major role in the decay of such gratings; readin g 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 sa mple was heated decayed within the same 10 K temperature range as the photo chromic absorption bands. As expected, undoped BGO shows a rapid dark decay at room temperature that becomes faster at higher temperatures. (C) 2001 A merican Institute of Physics.