Single Photon Counting With A Focus On Biomedical Applications

Over the past few years a growing number of companies have come to rely on Photon Counting for applications that range from particle sizing, atmospheric studies and advanced forms of biomedical research. Photon counting technology using Avalanche Photodiodes are achieving 70% photon detection efficiencies with sub nanosecond timing jitters and low dark counts (typically < 250cps).Besides being extremely small and rugged, these photon counting devices based on avalanche photodiodes have rapid recovery from overload, wide dynamic range and very low afterpulsing probabilities.

In biomedical instruments, fluorescence detection can be accomplished with simple photodiodes, photomultiplier tubes (PMT’s), Charged Couple Devices (CCD’s) and now photon counting devices. The detection technology depends on the performance and type instrument to be developed. For example, a simple florescence system would use a flash lamp to excite the sample and a simple detector (Silicon PIN or PMT) to detect the fluorescence intensity. For high throughput screening instrumentation, lasers and scanning optics are used to excite the multi-array plate and CCD’s to measure the intensity of all wells at once.