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By SensL

Low light detectors and multidetector imagers enable a wide range of applications ranging from cell imaging, biodiagnostic instrumentation, semiconductor wafer inspection, particle counting, nuclear medicine, radiation detection, and quantum cryptography, to low light imaging applications such as security cameras and light detection and ranging LIDAR systems. These application areas rely on the ability of the sensor to detect light levels, which range from the single photon (less than an attowatt) to millions of photons (picowatts to nanowatts) per second incident on the detector surface. The detector that has enabled these applications has traditionally been the photomultiplier tube, or PMT.

The PMT is a vacuum tube detector that uses a coated photocathode to convert incident photons into photoelectrons. The photoelectrons are then accelerated by the high electric field and their interaction with multiple metal dynodes in the PMT cause a shower of electrons, which are collected at the anode of the detector. The electrons are then read out as a current that indicates the level of light incident on the photocathode surface. Depending on the configuration of the PMT and the voltages that are applied, the PMT can operate in two specific modes of operation: single photon counting and analog or linear mode.