Integrated optic waveguides in gallium lanthanum sulfide glass for mid-IR applications

Abstract

Chalcogenide integrated optic (IO) waveguides operating in the mid-wave infrared (MWIR) are of interest for a variety of applications. They are potentially useful in compact MWIR laser sources for applications such as gas sensing and infrared countermeasures. Most work on chalcogenide integrated optics to date, however, has focused on arsenic sulfide, As2S3, or glasses with similar compositions. These glasses are known to suffer from a host of photo-induced effects including photo-darkening, photo-induced crystallization, and low optical damage thresholds. Furthermore, they can typically accept only low concentration of rare earth dopants without clustering or crystallization. Gallium lanthanum sulfide (GLS) is an alternative chalcogenide glass with great potential for use in IO devices operating in the MWIR. Like As2S3, GLS exhibits a large transparency window in the MWIR and high optical nonlinearity, but it does not suffer from the same type of photo-induced effects. High rare earth dopant concentrations without clustering are possible in GLS because rare earth ions substitute for lanthanum ions in the glass matrix. IO waveguides have previously been fabricated in GLS by several methods. Formerly, it was hypothesized that patterning GLS via reactive ion etching (RIE) was impossible do the presence of lanthanum and rare earth dopant ions, but we present results for GLS waveguides fabricated via RIE. In addition, we demonstrate 2.7 μm emission from Er3+-doped GLS waveguides resulting from erbium’s 4I11/2→4I13/2 transition.