Final published version
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Sensitivity Advantage of QCL Tunable-Laser Mid-Infrared Spectroscopy over FTIR Spectroscopy
AU - Childs, D.T.D.
AU - Hogg, R.A.
AU - Revin, D.G.
AU - Rehman, I.U.
AU - Cockburn, J.W.
AU - Matcher, S.J.
PY - 2015
Y1 - 2015
N2 - 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. © 2015 © David T. D. Childs, Richard A. Hogg, Dmitry G. Revin, Ihtseham Ur Rehman, John W. Cockburn, and Stephen J. Matcher.
AB - 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. © 2015 © David T. D. Childs, Richard A. Hogg, Dmitry G. Revin, Ihtseham Ur Rehman, John W. Cockburn, and Stephen J. Matcher.
KW - Fourier transform spectroscopy
KW - infra-red spectroscopy
KW - Infrared devices
KW - Infrared spectroscopy
KW - Light sources
KW - Optical tomography
KW - Quantum cascade lasers
KW - Quantum theory
KW - Semiconductor lasers
KW - Signal to noise ratio
KW - Spectroscopy
KW - Diffraction limited spatial resolution
KW - Hyperspectral Imaging
KW - Mid-infrared spectra
KW - Mid-infrared spectroscopy
KW - Spectral acquisition
KW - Supercontinuum light
KW - Thermal light sources
KW - Fourier transform infrared spectroscopy
U2 - 10.1080/05704928.2015.1075208
DO - 10.1080/05704928.2015.1075208
M3 - Journal article
VL - 50
SP - 822
EP - 839
JO - APPLIED SPECTROSCOPY REVIEWS
JF - APPLIED SPECTROSCOPY REVIEWS
SN - 0570-4928
IS - 10
ER -