Improvement of Output Stability of CO_2 Laser Pumped FIR Lasers by Using an Optical Isolator

摘要

Simultaneously oscillated 48-μm and 57-μm CH_3OD lasers pumped by a 9R(8) CO_2 laser have been developed for fusion plasma diagnostics. A back reflection from an optically pumped far-infrared (FIR) laser cavity affects not only the FIR laser stability but also the pump CO_2 laser stability. The back reflection has been reduced by an optical isolator using a quarter-wave plate and an absorbing thin-film reflector. As a result, we have achieved output stabilities of ±1.4%/h at the 48-μm laser and ±1.3%/h at the 57-μm laser.