Abstract

We investigate modal characteristics of a multilayer slab waveguide made on a Ti-diffused^1,2 LiNbO₃ substrate including a partially reflecting metal layer. This film is embedded between the diffused core and a dielectric buffer for obtaining low ohmic losses and stronger overlapping between optical and electric or acoustic driving fields in integrated optics devices. We consider the influence of four different kinds of metal (silver, gold, nickel, and aluminum), 200 Å thick, on propagation characteristics to assess the best waveguide structure. These metals at optical frequencies are modeled with a complex dielectric constant having negative real part ϵ_r More precisely we assume ϵ_Al= −47.56-j16.8, ϵ_Ag = −15.91-j0.52, ϵ_Ni = −10.44-j15, ϵ_Au = −10.22-j0.96. Furthermore in general they behave as weakly absorbing dielectrics so that the real part of the complex equivalent index n_eq = n — jk can be evaluated in a lossless approximation (ϵ_i = 0).

© 1983 Optical Society of America