Absorption loss and photorefractive-index changes in Ti:LiNbO_3 crystals and waveguides

Abstract
Measurement of optical absorption loss and photorefractive sensitivity (optically induced index changes) in Ti-diffused waveguides and bulk Ti-doped single crystals are reported. The absorption loss of strip guides is found to be 0.3 dB/cm at 0.633 μm, and this is expected to decrease at longer wavelengths. The results demonstrate that Ti impurities do not contribute to the absorption loss or to the photorefractive-index changes directly, rather these parameters are determined by impurities in the substrate crystal. A simple pyroelectric method for electrical adjustment of the optical input coupling is also reported.