Absolute frequency measurement of a lamb-dip stabilised water vapour laser oscillating at 10.7 THz (28 μm)

Abstract A 10.7 THz (28μm) water vapour laser has been stabilised to the Lamb dip. The centre frequency has been measured using an 0.89 THz (337 μm) hydrogen cyanide laser as a transfer oscillator and found to be 10718 068.71 ± 0.03 MHz (ie ± 3 × 10−9) over a wide range of operating conditions.