Time Gated Detection Technique Based On Single Photon Avalanche Photodiode

Single photon detector has been applied in many fields because of its high sensitivity in photoelectric detection.Single Photon Avalanche photodiode(SPAD)can produce high gain and is widely used in quantum communication,Raman detection,radar ranging and other fields.In this paper,the time gated detection system is based on the combination of single photon avalanche diode and single photon time coherent counter.Firstly,a set of fluorescence lifetime detection system based on gated quenching is designed and built,and by comparing with the active quenching scheme,it is proved that gated quenching has stronger suppression effect of post-pulse.The gated quenching scheme is to control the pulse width of synchronous telecommunication signal through the pulse drive circuit to realize different pulse widths to control the photon detection of SPAD and meet the test requirements of different samples.The gated quenching system was then used to test the fluorescence lifetime of Rhodamine 800 ethanol solutions,and detailed comparisons were made with the results of the self-built active quenching system and a commercial steadystate transient fluorescence spectrometer.The results show that for stable substances with short fluorescence lifetime(life interval within 10ns),the gated quenching scheme can suppress the measurement error to about 1.2% with the advantage of great inhibition of postpulse and dark count.Compared with active quenching,the error is reduced by more than 3times by using quenched chip to control the working state of SPAD.Due to the use of pulse drive circuit,the gating width of about 40 ns is obtained in the above work,which is far from enough for the Raman test system which needs to eliminate background fluorescence interference.In order to separate the Raman signal from the fluorescence signal in the time dimension,we need to use ultra-narrow gating to control the photon detection of SPAD.In this paper,an ultra-narrow pulse time gated detection system is designed,which uses a fast photodetector to convert picosecond laser pulses into electrical pulses and amplify and delay them.Finally,the minimum detection time of SPAD is about1 ns.In our experiment,we first measured the detection efficiency of SPAD through this scheme,and the results showed that high efficiency optical detection could be achieved in the band of 400～800nm.Then,the time of synchronization signal arriving at SPAD is precisely adjusted by optical retarder to realize the quantitative analysis of Raman fluorescence signal in time dimension.By testing the Raman fluorescence signal of ethanol and Rhodamine B ethanol solution,it is proved that the suppression of fluorescence signal can be effectively realized through the time-gated method,and the test of high Raman fluorescence signal-to-noise ratio can be obtained.This research proves that the time gated detection system based on SPAD has the potential to carry out Raman spectrum detection.