Photorefractive effects in proton exchanged LiTaO/sub 3/ optical waveguides

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Abstract
A circuit model is proposed to describe photorefractive effects in LiNbO/sub 3//LiTaO/sub 3/ channel waveguides at any intensity level. Capacitive charge storage at the waveguide boundaries is assumed to be provided by trapping states associated with photoconductivity. A consequence of this model is that photoconductive transients are independent of optical intensity at low intensity levels. Photovoltaic and photoconductive effects in proton exchange LiTaO/sub 3/ channel waveguides were experimentally investigated. Dark conductivities of 2*10/sup -15/ to 2 *10/sup -14/( Omega -cm)/sup -1/ were extrapolated from photoconductivities up to 2*10/sup -13/ ( Omega -cm)/sup -1/ for power levels of 0.1 to 3 mW. Large DC voltage dependent effects on the conductivity were observed. Straight channel waveguides were observed to be free of photovoltaic effects for output power levels below 35-75 mW.