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The Strathprints institutional repository is a digital archive of University of Strathclyde research outputs.

Strathprints serves world leading Open Access research by the University of Strathclyde, including research by the Strathclyde Institute of Pharmacy and Biomedical Sciences (SIPBS), where research centres such as the Industrial Biotechnology Innovation Centre (IBioIC), the Cancer Research UK Formulation Unit, SeaBioTech and the Centre for Biophotonics are based.

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Highly sensitive detection of trace gases using the time-resolved frequency downchirp from pulsed quantum-cascade lasers

McCulloch, Michael T. and Normand, Erwan L. and Langford, Nigel and Duxbury, Geoffrey and Newnham, D.A. (2003) Highly sensitive detection of trace gases using the time-resolved frequency downchirp from pulsed quantum-cascade lasers. Journal of the Optical Society of America B, 20 (8). pp. 1761-1768. ISSN 0740-3224

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Abstract

A spectrometer using a pulsed, 10.25-µm-wavelength, thermoelectrically cooled quantum-cascade distributed-feedback laser has been developed for sensitive high-resolution infrared absorption spectroscopy. This spectrometer is based upon the use of the almost linear frequency downchirp of up to 75 GHz produced by a square current drive pulse. The behavior of this downchirp has been investigated in detail using high-resolution Fourier-transform spectrometers. The downchirp spectrometer provides a real-time display of the spectral fingerprint of molecular gases over a wave-number range of up to 2.5 cm^-1. Using an astigmatic Herriott cell with a maximum path length of 101 m and a 5-kHz pulse repetition rate with 12-s averaging, absorption lines having an absorbance of less than 0.01 (an absorption of less than 1%) may be measured.