Photoconductivity and photovoltaic behaviour of LiNbO3 and LiNbO3 waveguides at high optical intensities

Abstract

The photoconductivity and photovoltaic currents of pure LiNbO3 and proton exchanged waveguides in LiNbO3 have been measured as a function of the optical intensity up to about several kW/cm2 by the use of surface electrodes. For pure LiNbO3 the observed dependences are a simple extrapolation of the well known low intensity behaviour. The photoconductivity of proton exchanged waveguides is considerably increased compared with pure LiNbO3 and the curves are strongly nonlinear in the high intensity region. These results can explain, at least qualitatively, the previously observed characteristic time and intensity dependence of light-induced refractive index changes in this type of waveguides. Both the time and temperature behaviour of the dark conductivity of all proton exchanged waveguides give strong evidence of ionic charge transport in the proton exchanged region.