Investigation of titanium- and copper-indiffused channel waveguides in lithium niobate and their application as holographic filters for infrared light

Abstract

Monomode channel waveguides for infrared light around 1550 nm are fabricated in lithium niobate by successive indiffusion of titanium stripes and thin evaporated layers of copper. The fabricated waveguides are optically characterized and investigated with an atomic force microscope. To evaluate the photorefractive properties holograms are recorded with green light of an argon ion laser and read in the various channels in reflection geometry with infrared light. The saturation values of the light-induced refractive-index change and the photoconductivity in the channels are measured. The results are consistent with a one-centre model for the charge transport. To demonstrate the multiplexing capabilities of the photorefractive waveguides three reflection holograms with 90% diffraction efficiency and a channel spacing of only 0.8 nm are superimposed in one sample.