BLOCKED IMPURITY BAND DETECTORS APPLIED TO TUNABLE DIODE-LASER SPECTROSCOPY IN THE 8-MU-M TO 28-MU-M RANGE

A novel tunable diode laser spectrometer operating at 8 < lambda < 28 mum is described. A blocked impurity band Si:As chip is employed as detector. This device operates in this wavelength range with high detectivity and adequate frequency response for the high-sensitivity techniques used. A combination of sweep averaging and second-harmonic detection at 22 kHz yielded signal-to-noise ratios of 1200 at lambda > 20 mum. The sensitivity and spectral resolution achieved are 1 order of magnitude better than those of Fourier instruments in this range, with an improvement in instrument time response of approximately 3000. Several molecular bands Of CO2 and N2O are observed for what is, to our knowledge, the first time with this instrument. Examples of spectral line measurements are presented.