9522740 Taylor The overall objective of this research is to obtain analytical and experimental results which support and promote the application of high-electrooptic-coefficient tungsten bronze ferroelectric materials ("super-EO materials") in a variety of guided wave optical devices. Techniques developed at Texas A&M for making the first low-loss waveguides and electrooptic modulators in tungsten bronze substrates will serve as the foundation for the proposed project. The waveguides are produced by a simple process in which static strain from a patterned surface film creates a localized refractive index increase. The Rockwell International Science Center, which has supplied super-EO materials to Texas A&M for several years, will continue in this collaborative role during the course of the proposed project. Research will be conducted in five critical task areas: (1) static strain optic (SSO) waveguide modeling, (2) device design, (3) material characterization, (4) modulator and switch development, and (5) tunable filter investigations. Two-dimensional refractive index profiles for TE and TM polarizations in SSO waveguides will be computed, considering both strain-optic and electrooptic contributions to the localized index change. A variation method will be utilized for waveguide mode analysis. Parameters needed for the waveguide and device models, such as strain-optic and electrooptic coefficients, refractive indices, and thermal expansion coefficients, will be measured. The recently discovered "self-poling" effect will be investigated experimentally to determine the conditions under which a large electrooptic effect is present without poling after processing of an SSO device at elevated temperatures. Electrooptic cutoff modulators, coupled waveguide switches, and tunable channel dropping filters which make use of the SSO waveguides will be designed, fabricated in the Rockwell substrates, and characterized. The proposed research will lay the groundwork for using super-EO materials in guided wave devices which could find increasing application in broadband communication networks over the next decade. Modulators and switches which exhibit order-of-magnitude improvement in performance over their counterparts in LiNbO3 - the traditional substrate of choice for guided wave electrooptic devices - will be sought. New channel-dropping filters for wavelength multiplexing with unprecedented tuning range, low crosstalk, and minimal electrical power dissipation will be explored. Successful demonstrations should reinforce Rockwell's expressed interest in commercializing the tungsten bronze substrates so that they will be generally available for research and device application. ***
