Review of a new IR nonlinear optical BaGa4Se7 crystal

A newly grown BaGa4Se7 crystal has been synthesized via the Bridgman-Stockbarger technique. This new crystal has advantages of high nonlinear optics (NLO) coefficients, high laser damage thresholds, and wide transparent regions. The BaGa4Se7 crystal has bright application prospects as a nonlinear gain medium in mid-infrared and terahertz regions. In this paper, the crystalline structure and synthetic method of the BaGa4Se7 crystal are introduced. The refractive indices and absorption coefficients along three dielectric axes between 0.1 THz and 1.0 THz are also obtained. The terahertz difference frequency generation (THz-DFG) characteristics based on the BaGa4Se7 crystal in the frequency range of 0.1 THz to 1.0 THz are analyzed theoretically and the phase-matching conditions are calculated. The application of BaGa4Se7 crystals in terahertz wave generation is also discussed.