Abstract
This study deals with the set-up of a high-accuracy and wavelength tunable mid-infrared light source. The light source includes Optical Parametric Oscillator (OPO), I2-stabilized Nd:YAG laser system, tunable offset locking system, optical frequency comb and frequency offset locking system. This light source is tunable in the mid-infrared ranging from 2.4 µm to 4.0 µm. The maximum power of the idler light is ~ 2 W. OPO pump frequency is determined by I2-stabilized Nd:YAG laser system and tunable offset locking system. OPO pump frequency is locked on I2-stabilized Nd:YAG laser system by offset locking technology, while OPO signal frequency is locked on optical frequency comb by offset locking technology. So the change in the pump frequency precisely controls the idler frequency. The OPO idler frequency accuracy can be enhanced by improving the OPO pump frequency. We have enhanced the OPO idler frequency accuracy to 8 kHz and sweep range to 3GHz by improving the OPO pump frequency. We have used this light source to measure the transition frequency of CH_4 P(7) F_2^((2)), In addition to correcting our system, it can also improve OPO idler frequency accuracy. We have also measured the transition frequency of H_3^+ R(1,0). The accuracy of the transition frequency is about 200 kHz or less, and the difference between the measurement results of ours and the other group is ~ 1 MHz or less.