hybrid detector, hybrid PMT, HPD, hybrid photomultiplier tube
A hybrid photo detector is a device for detecting very small amounts of light. Due to the low fluctuation, hybrid photodetectors are able to precisely determine the number of photoelectrons initially generated, as long as the maximum recording capacity is not exceeded. These detectors combine the properties of photomultipliers and avalanche photodiodes and provide a narrow pulse height distribution. For measurements in the time domain, this single amplification step leads to a regular propagation time spread and thus to low timing jitter.
Incoming photons are detected by an HPD using a photocathode (e.g. made of gallium arsenide phosphide), which emits a photoelectron with the highest possible quantum yield. This is strongly accelerated within a photomultiplier tube by means of high voltage in a vacuum, so that it finally hits an avalanche diode (electron bombardment). As a result, numerous electrons are released in the APD, so that the original photoelectron is duplicated more than a thousand times. In this way, measurable signals are generated that can be used for data acquisition.
Hybrid detectors have significantly lower dead times compared to PMTs or SPADs. Due to their high quantum efficiency, their large area (compared to SPADs), and fast time resolution these extremely light-sensitive detectors are commonly used in fluorescence lifetime microscopy and fluorescence correlation spectroscopy.