High-resolution absorption spectra of water vapor and acetylene detected by temperature tuning of laser diodes

A newly developed 0.78 μm single-mode laser diode spectrometer tuned by scanning the laser temperature with a resolution of better than 0.005 cm−1 is used to detect weak overtone spectra of water vapor and acetylene. A total of 3.65 nm continuous tuning range can be recovered from mode hops by operating two laser diodes alternately in different temperature regions at different injection current settings. The sensitivity of this spectrometer is demonstrated by its capability of detecting a weaker water vapor spectral line with an absolute intensity of 1.45×10−25 cm2/cm per molecule at 296 K using a 2.8 m single pass absorption cell by means of frequency-modulation spectroscopy.