Preparation and Characterization of Germanium Sulfide Based Sol-Gel Planar Waveguides

Abstract

Germanium sulfide based glass films have been deposited by spin-coating onto single crystal silicon wafers and silica glass disks, using the reaction between GeCl₄, either pure or doped with of 5 mol% of SbCl₃, dissolved in toluene, with H₂S. The films, heat-treated under different conditions, were characterized by X-ray diffraction, infrared spectroscopy, X-ray photoemission spectroscopy, mechanical profilometry and ellipsometry. Oxide contamination was found in these films, but this was reduced or even eliminated by a heat-treatment in H₂S gas, at ∼270°C. A maximum film thickness of ∼1.3 μm was achieved and the refractive indices of the films were in the range of ∼1.9–2.8 at 633 nm. Propagated light was observed by butt-coupling, for waveguides deposited on silica glass disks, at λ = 633 nm. Optical losses in the range of 1.1–1.9 dB/cm were measured at this wavelength, for different regions of different planar waveguides. The present method has achieved reasonably low loss and low levels of oxide contamination, which are promising for active applications.