High precision molecular laser frequency measurements using a THz frequency comb

Molecular lasers are powerful sources of continuous-wave THz radiation that can be used as local oscillators for heterodyne receivers. In this work we show that it is possible to measure precisely their emission frequency using a simple setup based on a THz frequency comb referenced to a microwave synthesizer. We show two examples: the first one is the measurement of the frequency of a NH
3
laser line around 2.029 THz and the second is the measurement of a D
2
O laser line around 2.450 THz.