Raman Spectroscopy Using Time-correlated Photon-counting Detection
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A highly sensitive, shot-noise-limited Raman signal acquisition is achieved using frequency-time transformation in a single-mode fiber and time-correlated photon counting system. To spectrally disperse Raman signal excited by a picosecond laser pulse, the light is directed into a sufficiently long single-mode fiber. The output end of the fiber is coupled into a time-gated photon multiplier tube (PMT). Due to a frequency-time conversion provided by the fiber core, photons of different frequencies experience different transient times. In this way, by measuring the photons' arrival time, Raman peaks can be recorded and separated. Moreover, in some cases the fluorescence background can be eliminated from Raman signals due to its much longer life-time. Consequently, a fluorescent background free Raman spectrum can be attained using the time-correlated photon-counting Raman spectroscopy. In this report, by using a 400m SM600 single-mode fiber and a Hamamatsu R3809U-50 PMT, we demonstrate the Raman spectrum of dimethyl sulfoxide excited by a short-pulsed laser. 2013 Copyright SPIE.
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Advanced Biomedical and Clinical Diagnostic Systems XI