THE POWER INCREASE AND ABSOLUTE FREQUENCY-STABILIZATION OF AN OPTICALLY-PUMPED FAR-INFRARED LASER

Far infrared (FIR) power more than or close to 100 mW has been obtaine d for FIR lines of CH3OH, HCOOH and CH3I gases from a FIR laser optica lly pumped by a 100-W CO2 laser, by adopting concave dichroic output c ouplers and adding a buffer gas. Frequency characteristics of the lase r were examined absolutely by harmonic-mixing the FIR with a millimete r wave from a PLL'ed Gunn oscillator on a Schottky barrier diode mixer . Short-term linewidths were less than 10 kHz (FWHM) and the frequency drift in free running was in the order of several hundreds of kHz dur ing 100 min. Absolute frequency stabilization was actively achieved fo r the FIR system by personal-computer (PC) aided feedback control, and a frequency stability of +/- 20 kHz was obtained in the experiment.