We present a spectroscopic system and an optical fibre probe which enable the full exploitation of the temporal evolution and spectral information of a weak Raman signal against background fluorescence and intrinsic fibre Raman. The system consists of a single multimode fibre and a CMOS single-photon avalanche diode (SPAD) line sensor capable of resolving and histogramming the arrival times of photons for 256 pixels simultaneously, offering improved signal to background compared to a non-time resolved measurement modality. The capabilities of the system are tested for intrinsic Raman standards such as cyclohexane and for pH sensing with functionalised gold nanoshells exploiting surface enhanced Raman scattering (SERS). The nanoshells are functionalised with the pH responsive 4-mercaptobenzoic acid (MBA) enabling demonstration of wide range pH sensing with low excitation power (< 1 mW) and short acquisition times (10 s), achieving a measurement precision of ± 0.07 pH units.
K. Ehrlich, H. Fleming, S. McAughtrie, A. Kufcsák, N. Krstajić, C. J. Campbell, R. K. Henderson, K. Dhaliwal, R. R. Thomson, and M. G. Tanner, "Time-resolved single photon spectroscopy through a single optical fibre for miniaturised medical probe design," Proc. SPIE 10685, Biophotonics: Photonic Solutions for Better Health Care VI, 106850Q (Presented at SPIE Photonics Europe: April 24, 2018; Published: 17 May 2018); https://doi.org/10.1117/12.2307334.
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