The photorefractive behavior of unannealed a-phase proton-exchanged LiNbO3 waveguides is studied. The time evolution of the diffraction efficiency η during recording strongly depends on the writing intensity. For an intensity of 79 W/cm2, a very sharp, transient peak of η appears initially followed by a decay to the saturation value. The peak is absent when writing is performed immediately after a complete optical erasure. The saturation value of η also present a peculiar dependence as a function of the writing intensity. The occurrence of shallow traps in these guides may explain qualitatively the observed behavior.
© 1999 Optical Society of AmericaPDF Article