Planar Multimode Fiber Optic Couplers.
Final technical rept. Jul 84-Apr 86,
TRW INC REDONDO BEACH CA ELECTRO OPTICS RESEARCH CENTER
Pagination or Media Count:
This report presents the results of our 1.75 years investigation of the fabrication of multimode star and access couplers in glass using the thallium-sodium ion exchange method. Four-port access and eight port transmission star couplers were fabricated on BK-7 glass. Electric-field-assisted thermal ion exchange was used to fabricate couplers. The photolithographic masks were designed with varying waveguide widths and mixing lengths. The best mask material was found to be silicon dioxide of 5000 angstroms thickness. Measurements were performed on efficiencies and distribution uniformities on both the single diffusion samples. Excellent first diffusion couplers were fabricated. Less than 0.2 dB and 1.0 dB non-uniformity in the splitting ratios were measured for the best first diffusion 2x2 and 4x4 couplers, respectively. Experiments were performed to bury the couplers below the surface of the glass with a second electric-field assisted diffusion for the purpose of reducing optical loss at the surface. Partially buried waveguides were formed but these wavequides exhibited greater scattering than the first diffusion waveguides. Author