EFFECTS OF OPTICAL BIAS ON MOVING GRATINGS IN BISMUTH SILICON-OXIDE AT LARGE FRINGE MODULATION

Optical bias has been applied in the formation of moving gratings in b ismuth silicon oxide at large fringe modulations. It is shown that opt ical bias is an effective method of overcoming the problems associated with the sudden drop in the optimum fringe velocity when the fringe m odulation is close to unity. It is experimentally found that within a certain range of optical bias the absolute diffraction efficiency can be higher than that without optical bias, which is not the case when a stationary grating is used. (C) 1996 Optical Society of America