Analyses of guiding properties of light-induced planar waveguides in LiNbO3:Fe crystals

To our knowledge, we first deduced the analytic expression of the indexchanged istribution in LiNbO3:Fe crystal induced by a Gaussian sheet beam considering th e photorefractive onecenter model and the photovoltaic charge carriers transp or tmechanism. A planar waveguide structure was fabricated by sheet beam illuminat ion employing the sandwich method in LiNbO3:Fe crystal. The index distribu tion i n the waveguide region was measured by using interferometric technique and the g uiding test was also performed. The rationality of the deduced analytic expression was demonstrated by the fitting results of the measured data point. Based on the ray equation, the guiding properties of the light-induced waveguide were analyzed by using numerical simulation. The results show that the interferom etric technique is valid for measuring the index distribution of waveguide with large width, and the guiding properties of the lightinduced waveguide structures depend on the waveguide width strongly. Using sheet beam with small width, planar waveguide structure with high quality can be fabricated in LiNbO3:Fe cryst al . And the analytic expression of the indexchangedistribution can be employed to predict the guiding properties of the lightinduced waveguide.