The photon detection efficiencies (PDE) of single photon avalanche diodes (SPADs) are investigated for practical applications such as LiDAR, time-of-flight 3D imaging, fluorescence microscopy, etc. After finding the dark count rate (DCR), radiation from a blackbody source is introduced through a light tube to the SPAD detector. Baffles are used in this tube to prevent light from reflecting off the side of the tube onto the detector. The PDE is then calculated knowing the light incident on the detector, the light detected by the detector, the DCR, and the afterpulsing probability. Measurements for several wavelengths, viz., 500, 615, 808, 900, and 940nm, various blackbody aperture diameters and temperatures, and different baffle diameters are reported. The results are then analyzed to find a range of these parameters that produce consistent results with each other, and compared with manufacturer specifications.
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