Abstract
An n-type InSb detector in intense magnetic fields has very sharp spectral responsivity due to the cyclotron resonance absorption, so that the wavelength giving a maximum response is tunable with the applied magnetic field.A far-infrared grating spectrometer of Czerny-Turner type, of which f-number is 3, using this tunable InSb detector has been designed and constructed in the frequency range from 33 to 333 cm-1.This spectrometer is very simple, for it has only two scatter plates and a cooled transmission filter to eliminate radiation of which energy is higher than the band gap energy of InSb.The spectral resolutions of this spectrometer are 0.3 cm-1 at 40 cm-1 and 0.4 cm-1 at 90 cm-1, respectively, which were measured under the constant magnetic field and with sufficiently higher S/N ratio and faster wavelength scanning time than those of conventional far-infrared grating spectrometers.Furthermore, the absorption spectra of water vapor are obtained by taking a tune between the maximum photoresponse of the InSb detector and the scanning of grating.
