PRECISION BROAD-BAND WAVEMETER FOR MILLIMETER AND SUBMILLIMETER RANGE

A precise, broadband, Fabry-Perot wavemeter has been designed and buil t to measure wavelengths in the millimeter and submillimeter range. Th e design of the wavemeter is novel in that it enhances the fundamental mode over a wide band and permits determination of the exact longitud inal index of the mode. With the use of an exact mode number in wavele ngth calculations, high measurement accuracies, to the extent permissi ble by the quality factor of the resonator, can be obtained. The wavem eter was tested by measuring well-known spectral lines of the OCS mole cule in the frequency range of 72-607 GHz. Measurement of 24 OCS lines demonstrated an accuracy of better than 2 x 10(-5) in relative units and 0.87 x 10(-5) in rms units for frequency/wavelength. A discussion of further development and automation of the wavemeter is included.