Frequency-Stabilized Mid-infrared Laser Source for Precision Spectroscopy^†

Precision measurements on molecules in the strong fundamental bands are of great importance. An accurate mid-infrared light source is a key for these studies. By locking the signal and pump light to an optical frequency comb, a high-precision continuous-wave optical parametric oscillator source is built, and the mid-infrared frequency drift is determined to be less than 1 kHz. As a demonstration, saturated absorption spectroscopy of the R(14) (00011)–(00001) line of ¹³CO₂ is measured, and the transition frequency is determined to be 68786813496(29) kHz. The frequency-stabilized mid-infrared laser source provides an opportunity for precision measurements of molecules in fundamental bands.