Towards standoff photothermal spectroscopy of CBRNE hazards using an ultra-fast tunable QCL

J. Miles; M. F. Muir; S. W. J. Scully; I. Hunter; C. McIlroy; J. E. Cunningham; C. V. Robinson; C. R. Howle

doi:10.1117/12.2558085

24 April 2020 Towards standoff photothermal spectroscopy of CBRNE hazards using an ultra-fast tunable QCL

J. Miles, M. F. Muir, S. W. J. Scully, I. Hunter, C. McIlroy, J. E. Cunningham, C. V. Robinson, C. R. Howle

Proceedings Volume 11416, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XXI; 114160A (2020) https://doi.org/10.1117/12.2558085
Event: SPIE Defense + Commercial Sensing, 2020, Online Only

Abstract

A stand-off photothermal sensor platform has been developed which combines two laser technologies: an external cavity Quantum Cascade Laser (EC-QCL), and a near-infrared laser Doppler vibrometer (NIR-LDV). The former is used as a 'pump' to induce vibrations/acoustic waves in the sample, whereas the latter is used to 'probe' these photothermal (PT) effects as the pump wavelength is varied; yielding spectral information on the target analyte. The EC-QCL uses an acousto-optic deflector (AOD) to obtain single-mode mid-infrared light of high output power with up to 1.6 µm of wavelength tuning. Using this AO based approach allows ultra-fast scanning across the full spectral bandwidth of the QCL gain chip at MHz rates, thus facilitating high speed identification of hazards. Initial validation of this pump-probe platform is demonstrated for the detection of 1,3-dinitrobenzene (DNB) and nitrobenzene (NB) on an aluminium substrate at a distance of several metres.

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J. Miles, M. F. Muir, S. W. J. Scully, I. Hunter, C. McIlroy, J. E. Cunningham, C. V. Robinson, and C. R. Howle "Towards standoff photothermal spectroscopy of CBRNE hazards using an ultra-fast tunable QCL", Proc. SPIE 11416, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XXI, 114160A (24 April 2020); https://doi.org/10.1117/12.2558085

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