Fabrication of Channel Waveguides in Chalcogenide Glass Films by a Focused Laser Beam

Abstract

We demonstrate a simple optical method for the fabrication of micrometer-width channel waveguides in chalcogenide glass (ChG) films, which does not require lift-off lithography. The method is based on photo-induced mass transport. For our experiments we use 400–600-nm-thick amorphous films of As₂S₃ and As₁₀Se₉₀ deposited in vacuum onto glass substrates. The waveguides are fabricated by a focused Ar ion laser beam (λ = 514 nm) with a waist diameter of ~0.7 μm. The positioning of the film in x-y-z-directions is controlled by computerized motor-driven stages whereby complex waveguide configurations can be drawn. For coupling of light (λ = 1.55 μm) between an optical fiber and the waveguide we used gratings, fabricated in the ChG, with a period of 0.8–1.5 μm and amplitude of 50–100 nm. The gratings are fabricated in an in-plane taper by laser illumination of the selected film area by two crossing p-polarized laser beams. We discuss mechanisms and kinetics of photo-induced mass transport in ChG films and possible contribution of viscous flow induced by a temperature gradient caused by the local heating of the film by the focused laser beam.