Stabilization of simultaneously oscillated 48- and 57-μm CH3OD lasers for plasma diagnostics

A two-color interferometer and polarimeter using simultaneously oscillated 48- and 57-μm CH₃OD lasers pumped by a 9R(8) CO₂ laser have been developed for future plasma diagnostics. Using a frequency-stabilized pump CO₂ laser and a twin type far-infrared (FIR) laser, the output power and the beat frequency have been stabilized by controlling the FIR laser cavity with a stepper motor. The stable two-color laser oscillation was enabled. The output power and beat frequency stabilities of the 48-μm laser were ±2.8 %/hour and 600±18 kHz_p-p/hour, respectively. The performances of the 57-μm laser were ±3.0 %/hour and 1200±18 kHz_p-p/hour.