IR-to-THz Down Conversion in Nonlinear GaSe:Al Crystals

The optical properties and hardness of GaSe, GaSe:Al, GaSe:S:Al, and GaSe:Al:O crystals are studied to create effective terahertz radiation generators. Doped crystals differ from pure GaSe in high mechanical and optical properties at a optimum doping level. Oxygen doping allows wide ranging changes in birefringence in the terahertz range.