Observation of saturation and rapid passage signals in the 10.25 micron spectrum of ethylene using a frequency chirped quantum cascade laser

M. T. McCulloch, G. Duxbury, N. Langford

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Rapid passage signals exhibiting saturation effects have been observed when a low-pressure sample of ethylene, within a multiple pass absorption cell, is subjected to radiation from a repetitively pulsed 10.25 micron quantum-cascade laser. Within each pulse the laser frequency sweeps 36GHz from high to low frequency in a time of 140 ns. At the low gas pressures, less than 20 mTorr, in the absorption cell the sweep rate through a Doppler-broadened absorption line (ca. 0.5 ns), is much faster than the collisional relaxation time of the ethylene and this leads to rapid passage effects. Examples are given of the complex rapid passage signals observed in pure and nitrogen broadened spectra. The rapid passage effects, which lead to the variety of the observed signals, have been modelled by numerical solution of the coupled Maxwell-Bloch equations for four sets of two-level systems.

Original languageEnglish
Pages (from-to)2767-2779
Number of pages13
JournalMolecular Physics
Volume104
Issue number16-17
DOIs
Publication statusPublished - 2006

Keywords

  • semiconductor diode-laser
  • population transfer
  • inversion
  • absorption
  • adiabatic passage
  • gases
  • spectrometer

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