Barium nonlinear optical crystals for the mid-IR: characterization and some applications

The linear and nonlinear optical properties of BaGa4S7, BaGa4Se7, BaGa2GeS6, and BaGa2GeSe6 are reviewed, highlighting their potential for frequency downconversion of powerful laser sources from the near- to the mid-IR. Examples of successful applications are summarized and briefly discussed.