Coupling characteristics for designing a LiNbO3 directional coupler fabricated by Ti diffusion have been investigated with a modified WKB method. The present analysis is verified by comparing the refractive-index change in the Ti-diffused LiNbO3 waveguide derived from direct measurement and coupling length calculation. Coupling length variations due to refractive-index change, diffusion length waveguide spacing, and wavelength are described. Tolerances in coupling length mismatch and propagation constant differences affecting cross talk of the directional coupler are discussed.
© 1981 Optical Society of America
Juichi Noda, Masaharu Fukuma, and Osamu Mikami, "Design calculations for directional couplers fabricated by Ti-diffused LiNbO3 waveguides," Appl. Opt. 20, 2284-2290 (1981)