Effective nonlinearity of the new quaternary chalcogenide crystal BaGa2GeSe6

The unknown magnitude and relative signs of the trigonal crystal ${\rm BaGa}_{2}{\rm GeSe}_{6}$BaGa₂GeSe₆ nonlinear coefficients have hindered defining an optimum orientation for maximum frequency conversion efficiency. This issue is resolved in the present work, obtaining ${d_{11}}= + {23.6}$d₁₁=+23.6, ${d_{22}}= - {18.5}$d₂₂=-18.5, and ${d_{31}}= + {18.3}\;{\rm pm/V}$d₃₁=+18.3pm/V for frequency doubling of the 10.591 µm radiation.