LPE GROWTH OF YTTRIUM-LUTETIUM, INDIUM-GALLIUM GARNET-FILMS FOR OPTICAL WAVE-GUIDE FORMATION ON A GGG SUBSTRATE

Yttrium-lutetium, indium-gallium garnet single-crystal films with a co mposition of {YxLu3-x} [Yy1Luy2Iny3Ga2-y1-y2-y3](Ga-3)O-12 (0 less tha n or equal to x less than or equal to 3, y1 = 0.02x, y2 = 0.12 - 0.04x , y3 = 1.08 - 0.11x) were grown on [1 1 1]- oriented GGG substrate by the LPE technique in order to fabricate a planar optical waveguide. Th e LPE growth results and optical properties of the films are reported. It was easy to control the composition of the film, because the distr ibution coefficients of the solutes showed gradual changes with the co mposition, and the coefficients ratios of Y/Lu and In/Ga, respectively , were 1.33-1.39 and 0.61-1.07. The films had high transparency in the visible and near-infrared regions. In this system, the addition of In increased and refractive index as a result of substitution on the Ga atom site. The films had a refractive index variation of similar to 0. 7% with the variation in the film composition, and this is large enoug h for optical waveguide fabrication. To evaluate its optical propagati on loss as a waveguide material, a slab waveguide, composed of core an d cladding layers, was formed on a GGG substrate. The propagation loss was 1.2 dB/cm at 1523 nm, indicating that the light was confined effe ctively in the waveguide with a low loss. (C) 1998 Elsevier Science B. V. All rights reserved.