Abstract
Directional couplers with relaxed design requirements for applications in guided wave Electro-Optic Tunable Filters (EOTFs) have been proposed and fabricated in x-cut LiNbO₃ using the Ti-indiffusion technique. The fabricated waveguides were characterized at a 1.55 mm optical wavelength using a DFB laser. Fabrication parameters have been identified for devices that satisfy the required criteria for the sum of power transfer coefficients being equal to one. Two bending angles (0.6⁰ and 1.0⁰) were used in the design. Power transfer coefficients as a function of the separation gap "d", with diffusion time as a parameter, have shown similar trends for these two design angles. However the bending loss at 1.0⁰ was generally larger than the one with a 0.6⁰ angle. The best fabrication parameters to achieve ([]TE + []TM = 1) are with a Ti film thickness of 1060-1100[], a separation gap of about 11[], and a diffusion temperature of 1025⁰C for 11-12 hours.
Gu, Donghua (2001). New beam splitter structure with relaxed constraints for electrooptic tunable filter. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2001 -THESIS -G8.