A. Onae et al., PRECISE FREQUENCY-MEASUREMENT OF A METHYL-ALCOHOL OPTICALLY-PUMPED LASER LINE AT 4.25 THZ, Optics communications, 109(1-2), 1994, pp. 81-85
Absolute frequency measurement of the 70.5 mum wavelength (4.25 THz) l
ine of a methyl alcohol (CH3OH) optically-pumped laser has been made b
y 47th-harmonic mixing with a Gunn diode (90 GHz) using a Nb-Nb point-
contact Josephson junction (JJ). The frequencies of the pump CO2 and t
he optically-pumped CH3OH lasers are locked, respectively, on the cent
er of the saturated absorption line of the methanol molecule and on th
e center of the FIR laser cavity pin curve. To accurately measure the
beat frequency from the JJ, a tracking oscillator is developed by mean
s of the phase-lock technique. The result of 4 251 674.63 +/- 0.15 (MH
z) is obtained for the center frequency of the optically-pumped laser
line. The accuracy of the measurement is 3.5 X 10(-8) and is about 5 t
imes more accurate than previous results.