Energy Transfer in an Optically Pumped D2O Gas THz Laser

Abstract

We report on the mid-infrared (MIR) and terahertz (THz) wave spectra of D2O gas pumped using a fundamental transverse mode transversely excited atmospheric CO2 laser with an emission wavelength of 9.26 μm. We obtain MIR emission lines at center wavelengths of 9.262, 9.491, and 9.752 μm, which correspond to the vibrational-energy-level-transition lines of D2O. We observe an intense THz stimulated Raman emission line of 385 μm and a weak cascade-transition line of 359 μm for transitions from rotational levels 422 to 413 and 413 to 404 in the first-excited vibration state of the D2O molecule gas. We establish a four-energy-level system for modeling the laser kinetics of the dual-wavelength (385 and 359 μm) superradiation THz laser. For the optically pumped D2O gas 385 μm THz laser, in considering the cavity effect and insertion loss of a THz cavity oscillator, an approximation treatment of the THz laser kinetics can be made based on a three-energy-level system.