In conventional PIN photodiodes, incoming photons create electron-hole pairs, also called charge carriers, which supply a measurable photocurrent. Avalanche photodiodes, APDs, differ from PIN detectors in that the charge carriers set free by the incoming light are accelerated by the internal electric field creating an avalanche of electron-hole pairs through impact ionisation.
The measurable photocurrent is much larger for an APD when compared to a PIN detector.
The SAR500-Series is based on a reach through structure for high sensitivity across the range 100-1100nm and features very fast response times as well as extremely low noise and dark current levels. The diameter of the active area of the SAR500S2 is 500 microns and the device are manufactured in a standard TO-46 can which is hermetically sealed.
These devices have long expected lifetimes making them suited for fit and forget applications such as range finding, LiDAR, spectroscopy and fluorescence.