Frequency tuning and efficiency enhancement of high power FIR lasers

Experimental and theoretical works have been carried out on a tunable far infrared (FIR) laser based on Raman scattering of tunable CO2 laser pump radiation in molecular gases. A theory of frequency tuning in laser pumped FIR lasers has been developed. The results of theoretical studies indicated that nearly continuous tuning should occur for pump intensity less than 10 MW/cm2. The results also predicted the existence of other effect such as ground state and two photon absorption, which can reduce the emission at certain FIR frequency. A new system of a 10 atm CO2 TE laser for pumping the superradiant FIR waveguide laser was constructed. The preliminary experimental results with this system showed good agreement with the theory. The possibility of achieving enhanced FIR laser efficiency by the simultaneous emission of many photons was considered. These processes achieve high efficiency through the simultaneous emission of several low frequency photons for each high frequency photon absorbed. (Kato, T.)