Highly efficient and compact cavity oscillator for high-power, optically pumped gas terahertz laser

We demonstrate a highly efficient and compact terahertz cavity oscillator that is based on z-cut crystal quartz used as the dichroic beam splitter, for the first time to the best of our knowledge. With D2O gas as the active medium, pumped with a multitransverse mode TEACO₂ laser, experimental verification was also presented to demonstrate the advantages of this cavity oscillator. With the cavity length of 120 cm, 7.4 mJ pulse energy at pulse repetition frequency of 6 Hz, pulse width of 90 ns, and peak power of 82.2 kW were achieved at a wavelength of 385 ìm. Photon conversion efficiency (PCE) of 44% was obtained at the maximum output level from this terahertz cavity oscillator. Furthermore, to our knowledge, this PCE is the highest efficiency ever reported in D2O gas, 385 ìm terahertz cavity laser systems. The beam quality or M2 factor was found to be about 1.77.