Time-resolved Raman spectroscopy using a CMOS SPAD array to remove fluorescent and fibre Raman backgrounds

Raman spectroscopy is limited by weak signals, fluorescence interference, and fibre-induced backgrounds. To address this, a 512-pixel complementary-metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) line sensor array with on-chip timing electronics was employed to enable the detection of weak Raman signals and use time gating to suppress background fluorescence and fibre-induced Raman signal. The functionality of this compact optical system is initially demonstrated in a free space setup, achieving an improved signal enhancement within shorter measurement times of 30 s. Finally, to support the development of miniaturised single fibre based Raman probes, the removal of fibre background is demonstrated through remote detection of paracetamol and other samples using time-gating and a 1 m 50 µm core multimode fibre.