Sensitivity advantage of QCL tunable-laser mid-infrared spectroscopy over FTIR spectroscopy

Childs, D. T. D. , Hogg, R. A. , Revin, D. G., Rehman, I. U., Cockburn, J. W. and Matcher, S. J. (2015) Sensitivity advantage of QCL tunable-laser mid-infrared spectroscopy over FTIR spectroscopy. Applied Spectroscopy Reviews, 50(10), pp. 822-839. (doi: 10.1080/05704928.2015.1075208)

Abstract

Interest in mid-infrared spectroscopy instrumentation beyond classical FTIR using a thermal light source has increased dramatically in recent years. Synchrotron, supercontinuum, and external-cavity quantum cascade laser light sources are emerging as viable alternatives to the traditional thermal black-body emitter (Globar), especially for remote interrogation of samples (“stand-off” detection) and for hyperspectral imaging at diffraction-limited spatial resolution (“microspectroscopy”). It is thus timely to rigorously consider the relative merits of these different light sources for such applications. We study the theoretical maximum achievable signal-to-noise ratio (SNR) of FTIR using synchrotron or supercontinuum light vs. that of a tunable quantum cascade laser, by reinterpreting an important result that is well known in near-infrared optical coherence tomography imaging. We rigorously show that mid-infrared spectra can be acquired up to 1000 times faster—using the same detected light intensity, the same detector noise level, and without loss of SNR—using the tunable quantum cascade laser as compared with the FTIR approach using synchrotron or supercontinuum light. We experimentally demonstrate the effect using a novel, rapidly tunable quantum cascade laser that acquires spectra at rates of up to 400 per second. We also estimate the maximum potential spectral acquisition rate of our prototype system to be 100,000 per second.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Childs, Dr David and Hogg, Professor Richard
• Authors: Childs, D. T. D., Hogg, R. A., Revin, D. G., Rehman, I. U., Cockburn, J. W., and Matcher, S. J.
• College/School: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Journal Name: Applied Spectroscopy Reviews
• Publisher: Taylor & Francis
• ISSN: 0570-4928
• ISSN (Online): 1520-569X
• Copyright Holders: Copyright © 2015 The Authors
• First Published: First published in Applied Spectroscopy Reviews 50(10):822-839
• Publisher Policy: Reproduced under a Creative Commons License