  An ultrashort-pulse Cr^{2+}:ZnSe laser is a novel broadband source for
sensitive high resolution molecular spectroscopy. A 130-fs pulse allows
covering of up to 380 cm^-1 spectral domain around 2.4 $\mu$m which is analyzed
simultaneously with a 0.12 cm^-1 (3.6 GHz) resolution by a Fourier-transform
spectrometer. Recorded in 13 s, from 70-cm length absorption around 4150 cm^-1,
acetylene and ammonia spectra exhibit a 3800 signal-to-noise ratio and a
2.4*10^-7 cm^-1*Hz^-1/2 noise equivalent absorption coefficient at one second
averaging per spectral element, suggesting a 0.2 ppbv detection level for HF
molecule. With the widely practiced classical tungsten lamp source instead of
the laser, identical spectra would have taken more than one hour.
