High-speed high-sensitivity infrared spectroscopy using mid-infrared swept lasers
(Conference Presentation)

David T. D. Childs; Kristian M. Groom; Richard A. Hogg; Dmitry G. Revin; John W. Cockburn; Ihtesham U. Rehman; Stephen J. Matcher

doi:10.1117/12.2209300

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28 June 2016 High-speed high-sensitivity infrared spectroscopy using mid-infrared swept lasers (Conference Presentation)

David T. D. Childs, Kristian M. Groom, Richard A. Hogg, Dmitry G. Revin, John W. Cockburn, Ihtesham U. Rehman, Stephen J. Matcher

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Proceedings Volume 9720, High-Speed Biomedical Imaging and Spectroscopy: Toward Big Data Instrumentation and Management; 97200V (2016) https://doi.org/10.1117/12.2209300
Event: SPIE BiOS, 2016, San Francisco, California, United States

Abstract

Infrared spectroscopy is a highly attractive read-out technology for compositional analysis of biomedical specimens because of its unique combination of high molecular sensitivity without the need for exogenous labels. Traditional techniques such as FTIR and Raman have suffered from comparatively low speed and sensitivity however recent innovations are challenging this situation. Direct mid-IR spectroscopy is being speeded up by innovations such as MEMS-based FTIR instruments with very high mirror speeds and supercontinuum sources producing very high sample irradiation levels. Here we explore another possible method – external cavity quantum cascade lasers (EC-QCL’s) with high cavity tuning speeds (mid-IR swept lasers). Swept lasers have been heavily developed in the near-infrared where they are used for non-destructive low-coherence imaging (OCT). We adapt these concepts in two ways. Firstly by combining mid-IR quantum cascade gain chips with external cavity designs adapted from OCT we achieve spectral acquisition rates approaching 1 kHz and demonstrate potential to reach 100 kHz. Secondly we show that mid-IR swept lasers share a fundamental sensitivity advantage with near-IR OCT swept lasers. This makes them potentially able to achieve the same spectral SNR as an FTIR instrument in a time x N shorter (N being the number of spectral points) under otherwise matched conditions. This effect is demonstrated using measurements of a PDMS sample. The combination of potentially very high spectral acquisition rates, fundamental SNR advantage and the use of low-cost detector systems could make mid-IR swept lasers a powerful technology for high-throughput biomedical spectroscopy.

Conference Presentation

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David T. D. Childs, Kristian M. Groom, Richard A. Hogg, Dmitry G. Revin, John W. Cockburn, Ihtesham U. Rehman, and Stephen J. Matcher "High-speed high-sensitivity infrared spectroscopy using mid-infrared swept lasers (Conference Presentation)", Proc. SPIE 9720, High-Speed Biomedical Imaging and Spectroscopy: Toward Big Data Instrumentation and Management, 97200V (28 June 2016); https://doi.org/10.1117/12.2209300

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