Optical bias has been applied in the formation of moving gratings in bismuth silicon oxide at large fringe modulations. It is shown that optical bias is an effective method of overcoming the problems associated with the sudden drop in the optimum fringe velocity when the fringe modulation 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.
Wang, Z. Q., Cartwright, C. M., Gillespie, W. A., & Cook, N. J. (1996). Effects of optical bias on moving gratings in bismuth silicon oxide at large fringe modulation. Applied Optics, 35(20), 3829-3834. https://doi.org/10.1364/AO.35.003829