[1] A. Ashkin, G. D. Boyd, J. M. Dziedzic, R. G. Smith, A. A. Ballman, J. J. Levinstein and K. Nassau, “ Optically induced refractive index inhomogeneities in LiNbO3 and BaTiO3”, Appl. Phys. Lett. 9,72-74(1966)
[3] William B. Lawler, Christopher J. Sherman, and M. G. Moharam ”Direct measurement of the amplitude and the phase of photorefractive field in KNbO3:Ta and BaTiO3” J. Opt. Soc. Am.B Vol. 8, NO. 10 October 1991
[4] R. Grousson, M. Henry, S. Mallick, and S. L. Xu “Measurement of bulk photovoltaic and photorefractive characteristics of iron doped LiNbO3”,J. Appl. Phys. 54(6),3012(1983)