Aging behavior of photo-induced As/sub 2/S/sub 3/ gratings

Abstract

Summary form only given. Amorphous chalcogenide glass (ChG) films are candidates for passive and active photonic devices for applications in infrared integrated optical systems as they exhibit high transparency in the 1-10 /spl mu/m wavelength region, a large nonlinear refractive index, and low phonon energies. ChGs are photosensitive when exposed to bandgap energy (E/sub g//spl sim/2.35 eV for As/sub 2/S/sub 3/). Use of these photosensitive effects (photodarkening and photoexpansion) in ChGs, allows the creation of bulk waveguide structures, or the patterning of photoinduced relief gratings and guided wave structures in ChG films. The ultimate long-term stability of such optical elements relies on the generation of photo-induced structures which undergo limited structural relaxation with time. ChGs typically exhibit lower glass transition temperatures (T/sub g/) than oxide glasses and hence, can exhibit significant sub-T/sub g/ relaxation at, or near, room temperature. This relaxation can result in structural changes that modify the as-written glass structure and performance of the optical element. This paper reports results of Raman analysis of As/sub 2/S/sub 3/ films and gratings aimed at identifying specific bonding changes, which accompany the aging process.