Electrooptic Bragg-deflection modulators: theoretical and experimental studies.

We have studied the mechanism of Bragg diffraction in electrooptic thin-film lightguides and examined in detail the effectiveness of interaction between the electric field and optical field. Expressions for the full deflection voltage and the power per bandwidth are obtained and applied to various modulator structures using out-diffused, metal-diffused, epitaxial, and sputtered-film (electrooptic substrate) waveguides. An expression for minimum interaction length to ensure better than 30-dB extinction ratio is derived. The theoretical results are checked with experimental observations from an electrooptic substrate modulator we fabricated, and good agreement is obtained.