Blocked impurity band detectors applied to tunable diode laser spectroscopy in the 8- to 28-microm range

A novel tunable diode laser spectrometer operating at 8 < lambda < 28 microm 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 microm. 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 ~ 3000. Several molecular bands of CO(2) and N(2)O are observed for what is, to our knowledge, the first time with this instrument. Examples of spectral line measurements are presented.