Frequency measurement at 4.25 THz (70.5μm) using a Josephson harmonic mixer and phase-lock techniques

A direct frequency measurement has been made on the 70.5 mu m wavelength line of the methyl alcohol optically-pumped laser by 43rd-harmonic mixing with a klystron using a point-contact Josephson junction. It was possible to phase-lock the klystron to the laser. The centre frequency of the emitted radiation when the CO 2 pump laser (9.68 mu m, P(34)) was tuned near the absorption line centre was found to be 4251 674.0+or-0.7 MHz. This result is about 5 MHz higher than an earlier published result by Petersen et al. (1975). A result is also given for the frequency of the 118-8 mu m wavelength line in methyl alcohol.