Sol-gel derived germanium sulfide planar waveguides

In active integrated optics applications for 1.3 mum involving Pr3+ doping, a low vibrational energy sulfide-based glass matrix is desirable, in order to increase the quantum efficiency of the Pr3+ emission. This paper demons trates the feasibility of preparing germanium sulfide planar waveguides via sol-gel processing. A two-step method was used: (1) germanium oxide gel fi lms were deposited by spin-coating onto single-crystal silicon wafers or si lica glass substrates, using germanium ethoxide as the precursor; (2) the g el films were then heat treated in a H2S atmosphere, under different condit ions. Infrared and Raman spectroscopies, X-ray photoemission spectroscopy ( XPS), X-ray diffraction and scanning electron microscopy (SEM) were used, i n order to characterize the purity and structure of the films. The residual oxide content was found to be low (similar to2%). Film thickness and refra ctive index were measured by mechanical profilometry and ellipsometry. The occurrence of propagating modes and their respective optical losses were al so investigated at 633 nm, using either prism-coupling, or butt-coupling me thods. (C) 2001 Published by Elsevier Science Ltd.