A Study of Effective Nonlinearity of BaGa2GeS6 Crystal by CO Laser Sum-Frequency Generation with Type-I and Type-II Phase Matching

Abstract: The sum-frequency generation of broadband CO laser radiation (λ ≈ 5–6 μm) in a new nonlinear BaGa2GeS6 crystal at type I and II phase matching at the variation of polar and azimuth angles of this crystal has been experimentally investigated. A small mismatch (~3°) between the values of measured and calculated phase matching angles was found. Also, based on experimental data and their comparison with calculations, a set of coefficients was determined of the nonlinear susceptibility tensor of BaGa2GeS6, which best describes the experimental results. © 2025 Elsevier B.V., All rights reserved.