Single-Mode GaInAsP Optical Waveguides*

Abstract

There is considerable interest in the development and applications of GaInAsP/InP sources and detectors. However, there has been no report to date of single-mode guided-wave optical components in this materials system. Such guided structures are necessary to develop contemplated monolithic structures where on-chip waveguiding is used to switch, modulate or direct light between sources and detectors. We report here the fabrication and testing of the first single-mode GaInAsP optical waveguides. The devices fabricated are rib guides formed on low-concentration LPE layers grown on InP substrates. The propagation loss is found to be 1.7 cm−1 at 1.3 µm and 2.3 cm−1 at 1.15 µm for layers with a 0.99-µm bandgap. While these losses are not as low as the 0.5 cm−1 value obtained for oxide-confined GaAs guides,1 the values are comparable to those obtained for single-mode heterostructure GaAlAs waveguides,2 and are the initial measurements of below-band-edge absorption in GaInAsP.