Backscatter WERS for trace chemical analyte detection using a handheld spectrometer

N. F. Tyndall; D. A. Kozak; M. W. Pruessner; R. A. McGill; C. A. Roberts; T. H. Stievater; B. L. Miller; E. Luta; M. Z. Yates; E. D. Emmons; P. G. Wilcox; J. A. Guicheteau

doi:10.1117/12.2559641

24 April 2020 Backscatter WERS for trace chemical analyte detection using a handheld spectrometer

N. F. Tyndall, D. A. Kozak, M. W. Pruessner, R. A. McGill, C. A. Roberts, T. H. Stievater, B. L. Miller, E. Luta, M. Z. Yates, E. D. Emmons, P. G. Wilcox, J. A. Guicheteau

Author Affiliations +

Proceedings Volume 11416, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XXI; 1141603 (2020) https://doi.org/10.1117/12.2559641
Event: SPIE Defense + Commercial Sensing, 2020, Online Only

Abstract

Waveguide-enhanced Raman spectroscopy (WERS) enables the detection and identification of trace concentrations of vapor-phase analytes using a functionalized chip-scale photonic circuit. Here, we show that WERS signal can be collected from part-per-billion levels of targeted analytes in a backscatter geometry, which, compared to forward-scatter, simplifies component integration and is more tolerant of waveguide loss and modal interference. In addition, we discuss our progress towards a compact Raman sensing system that incorporates a handheld spectrometer and chip-scale optical filters. We demonstrate that a handheld, thermo-electrically cooled spectrometer can be used for backscatter WERS with a comparable signal-to-noise to that of a liquid-nitrogen cooled benchtop spectrometer. Finally, we describe efforts to integrate the dichroic Raman filter on-chip using arrays of unbalanced Mach-Zehnder interferometers. Measurements show filter performance sufficient for integration with WERS: Transmission of >80% of the laser in the cross port and Stokes signal in the through port; and extinction of the laser by >20 dB in the though port and of Stokes signal by >8 dB in the cross port.

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N. F. Tyndall, D. A. Kozak, M. W. Pruessner, R. A. McGill, C. A. Roberts, T. H. Stievater, B. L. Miller, E. Luta, M. Z. Yates, E. D. Emmons, P. G. Wilcox, and J. A. Guicheteau "Backscatter WERS for trace chemical analyte detection using a handheld spectrometer", Proc. SPIE 11416, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XXI, 1141603 (24 April 2020); https://doi.org/10.1117/12.2559641

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