Effective Nonlinearity of BaGa2GeSe6: A Promising Quaternary Chalcogenide Crystal for the Mid-IR

We determine the magnitude and relative sign of the nonlinear coefficients of the low-symmetry trigonal nonlinear crystal BaGa 2 GeSe 6 : d 11 = +23.6, d 22 = −18.5, and d 31 = +18.3 pm/V, opening the way for maximizing d eff and broad applications.