Control of Melt Decomposition for the Growth of High Quality AgGaGeS4 Single Crystals for Mid-IR Laser Applications

AgGaGeS4 (AGGS) is a promising nonlinear crystal for mid-IR laser applications which could satisfy the lack of materials able to convert a 1.064 μm pump signal (Nd:YAG laser) to wavelengths higher than 4 μm, up to 11 μm. The processing steps of this material are presented in this study. The key issue of AGGS crystal processing is the control of decomposition at high temperature due to the high volatility of GeS2. This study presents solutions to obtain high quality single crystals. AGGS ingots with 28 mm diameter and 70 mm length were grown by the Bridgman–Stockbarger method. The crystals have good homogeneity and high transparency in the 0.5–11.5 μm spectral range, making them suitable for optical experiments. The influence of GeS2 volatility on melt stoichiometry during the AgGaGeS4 processing is outlined, and solutions to improve the crystals quality are presented.