Vapor deposited Cr-doped ZnS thin films: Towards optically pumped mid-infrared waveguide lasers

Abstract

Compact, affordable mid-IR lasers require the development of gain materials in waveguide form. We report on the high vacuum deposition of Cr:ZnS films with concentration ranging from 1018-1020 dopants/cm3 . At low concentrations, films display wellisolated absorption associated with substitutional Cr2+ ions in the lattice. Spatial modulation of the dopant concentration suppresses the absorption associated with this substitution. Lateral crystallite sizes less than 30 nm are associated with the lowest substrate temperatures (<50 °C) used during deposition, and waveguide losses as low as 8dB/cm are observed. These materials are promising candidates as gain media for fabrication of waveguide mid-IR lasers.