Fast Plastic Detection with a Time-Resolved Raman Spectrometer

The performance of a time-resolved Raman spectrometer equipped with a new CMOS SPAD (single-photon avalanche diode) sensor was studied in fast detection of common plastic types. Sixteen samples, including transparent, white, and colored pieces of polyethylene, polypropylene, polyethylene terephthalate, and polystyrene were measured with different acquisition times and all measurements were repeated 200 times for detection probability calculations. When a time gate width of 450 ps was applied to reject the fluorescence emission, a 99% detection probability was achieved for transparent and white samples with the acquisition time of
$\mathbf{250} \ \boldsymbol{\mu}\mathbf{s}$
. With colored samples, a 10-ms acquisition time was required to get at least a 99% detection probability for all the samples. For most of the samples, the acquisition time could be reduced when 450 ps time gate width was used instead of 3-ns time gate. For highly fluorescent samples, the reduction in required acquisition time was more than 90%.