Research on the Key Components of a 2.5 THz Methanol Laser and the Optical Design of an ICP Source for Interferometry

Lasers that emit THz light using CO2 laser-pumped gas molecules are widely used as light sources for polarimeter-interferometer diagnostic systems in plasma fusion devices because of their continuous, stable, high-power output. The 2.5THz optically pumped methanol gas laser is considered suitable as a polarimeter/interferometer light source for future high-performance plasmas due to its shorter wavelength and larger output power. In this paper, a methanol gas laser, optically pumped for plasma interferometry, has been established. The deviation of the incident and azimuth angles of the Brewster window of the laser cavity pump light input window is within 5 and 10 degrees, respectively, which has little effect on the transmission of the pump beam. Studies of output couplers show that selecting the appropriate output aperture is crucial for achieving the highest THz output. Additionally, an interference optical path is designed to measure the electron density of the ICP source, which will verify the feasibility of the 2.5THz interferometer.