The Quantum cascade (QC) laser is an entirely new type of semiconductor device in which the laser wavelength depends on the band-gap engineering. It can be made to operate over a much larger range than lead salt lasers, covering significant parts of both the infrared and submillimetre regions, and with higher output power. In this tutorial review we survey some of the applications of these new lasers, which range from trace gas detection for atmospheric or medical purposes to sub-Doppler and time dependent non-linear spectroscopy.
"IR quantum cascade laser absorption spectroscopy (QCLAS), exploiting the internal frequency sweep of the laser  , may provide both access to chemical kinetic processes of IR active compounds in plasmas and a theoretical time resolution equal to the nanosecond pulse width of the laser. Non-linear absorption phenomena which are observed under low-pressure conditions   may be taken into account in plasma diagnostics by a careful calibration . Recently, a pulsed Ar(+N 2 )/NO dc discharge has been investigated by means of time-resolved QCLAS . "
[Show abstract][Hide abstract] ABSTRACT: Time-resolved quantum cascade laser absorption spectroscopy at 1897 cm−1 (5.27 µm) has been applied to study the NO(X) kinetics on the micro- and millisecond time scale in pulsed low-pressure N2/NO dc discharges. Experiments have been performed under flowing and static gas conditions to infer the gas temperature increase and the consequences for the NO line strength. A relatively small increase of ~20 K is observed during the early plasma phase of a few milliseconds. After some 10 ms gas temperatures up to 500 K can be deduced. The experimental data for the NO mixing ratio were compared with the results from a recently developed time-dependent model for pulsed N2–O2 plasmas which are well in accord. The early plasma pulse is determined by vibrational heating of N2 while the excitation of NO(X) by N2 metastables is almost completely balanced. Efficient NO depletion occurs after several milliseconds by N atom impact.
[Show abstract][Hide abstract] ABSTRACT: The same quantum cascade laser spectrometer working around 9μm was used in both continuous-wave and pulsed modes to compare
their own characteristics. The laser emitting in continuous-wave mode was mainly used to study some spectroscopic parameters
of SO2 ro-vibrational lines. This work demonstrates the necessity to use new calculations previously developed instead of conventional
databases such as HITRAN. In addition, the same laser emitting in pulsed mode with long pulses (600 to 900ns) was used to
record SO2 spectra with the intrapulse technique. This work permits us to make comparisons about those two modes of emission for the
development of future spectrometers.
Applied Physics B 02/2007; 90(2):177-186. DOI:10.1007/s00340-007-2857-6 · 1.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper we investigate the performance of quantum cascade (QC) lasers for high frequency modulation spectroscopy, particularly
using frequency modulation (FM) and two-tone (2T) techniques. The coupling of the rf signal to the QC laser through the cryostat
is studied in detail as well as the noise contributions of both the detector and the laser source to the final spectra. The
experimental traces are obtained by spectroscopy on low-pressure N2O and CH4 gases at 8.0μm and 7.3μm wavelength, respectively, and reproduce the line profiles predicted by theory. As a preliminary
result, an enhancement of a factor six is measured with respect to direct absorption line recording.
Applied Physics B 11/2006; 85(2):223-229. DOI:10.1007/s00340-006-2343-6 · 1.86 Impact Factor
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