Experimental Evaluation of Drift and Nonlinearities in Lithium Niobate Interferometric Modulators

摘要

This paper presents quantitative measurements of two nonideal characteristics of lithium niobate integrated optical devices: nonlinear electrooptic phase modulation and the photo-refractive effect. These effects can occur in any lithium niobate channel-waveguide phase modulator or passive channel waveguide, and may affect the performance of any device that uses these basic building blocks. The measurements described in this paper were performed by means of an integrated-optical Mach-Zehnder interferometer which consists of passive channel waveguides and phase modulators. We have measured a quadratic term in the phase shift vs voltage relation for electrooptic phase modulation. We have also measured the photorefractive effect at wavelengths of 0.85, 1.06, and 1.3 micrometers, using y- and z-propagation. We evaluate both photovoltaic and photoconductive effects, and give estimates for the constants in a simple model that describes the photorefractive effect. Reprints. (aw)