LPE growth of yttrium–lutetium, indium–gallium garnet films for optical waveguide formation on a GGG substrate

Abstract

Yttrium–lutetium, indium–gallium garnet single-crystal films with a composition of { Y x Lu 3−x}[ Y y1 Lu y2 In y3 Ga 2−y1−y2−y3]( Ga 3) O 12 (0⩽x⩽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. The LPE growth results and optical properties of the films are reported. It was easy to control the composition of the film, because the distribution coefficients of the solutes showed gradual changes with the composition, 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 ∼0.7% with the variation in the film composition, and this is large enough for optical waveguide fabrication. To evaluate its optical propagation loss as a waveguide material, a slab waveguide, composed of core and 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 effectively in the waveguide with a low loss.