Intra-Pulse Spectroscopy Based on Room-Temperature Pulsed Quantum-Cascade Laser for N2O Detection

Mid infrared lasers are very suitable for high sensitive trace gases detection in that their wavelengths cover the fundamental absorption lines of most gases, Quantum cascade lasers have been demonstrated to be ideal light sources with their especially high power, wide range of tuning capability and favorable operating condition on room temperature. The intra-pulse spectroscopy based on a room-temperature distributed-feedback pulsed QC laser is a simple and effective trace gas detective method to detect trace-gas qualitatively or quantificationally. When a long excitation pulse is applied to a QC laser, the laser frequency tunes almost linearly to lower wave number (lower frequency) as a function of time so all absorption spectral elements are recorded during a single laser pulse In the present paper the method was introduced, and identification of N2O spectral fingerprint using this spectroscopy was demonstrated experimentally. The thermal chirp from a 500 ns long excitation pulse was applied to a quantum-cascade laser to get a fast wavelength.,canning. thus a wave number tuning of about 1 cm(-1) was produced. The N2O absorption spectrum centered at 1273.7 cm(-1) was also obtained. The measured absorption spectrum is consistent with HITRAN data precisely.