ZnGa2Se4, a nonlinear material with wide mid infrared transparency and good thermomechanical properties

Abstract

During the last decades, mid-infrared (3–12 μm) laser sources using crystals with nonlinear optical properties have attracted a particular attention due to their potential applications in different fields such as optical counter-measures and remote chemical sensing. As transparency of common oxide crystals is limited to about 4 μm, many researches have been focused on chalcopyrite compounds because of their wide transparency in the mid-IR range and their strong nonlinear optical coefficients. There is a need of such crystals able to convert efficiently the near infrared wavelengths from commercially available lasers into wavelengths higher than 5 μm through Optical Parametric Oscillators (OPO) systems. This paper presents a new compound: ZnGa2Se4 (ZGSe). Measurements made on dense polycrystals show a high thermal conductivity value in comparison with other selenides (2.9 W m−1 K−1), a wide transparency from visible to beyond the band III of the mid IR (0.6 μm–17 μm) and a coefficient of thermal expansion inferior to 10−5 K−1. These results are very encouraging and improvements of the growth process are now undertaken to obtain single crystals with the required optical quality.