A pulsed quantum-cascade distributed feedback laser operating at near room temperature was used for sensitive high-resolution IR absorption spectroscopy of ambient air at a wavelength of ˜8 mm. Neartransform- limited laser pulses were obtained owing to short (˜5-ns) current pulse excitation and optimized electrical coupling. Fast and slow computer-controlled frequency scanning techniques were implemented and characterized. Fast computer-controlled laser wavelength switching was used to acquire second-derivative absorption spectra. The minimum detectable absorption was found to be 3 × 10−4 with 105 laser pulses (20-kHz repetition rate), and 1.7 × 10−4 for 5 × 105 pulses, based on the standard deviation of the linear regression analysis.
All Science Journal Classification (ASJC) codes
- Engineering (miscellaneous)
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering