Photon-Based Detectors

see also:

photonic quantum sensing, APDs, SPADs, PMTs

In the context of photonic quantum sensing, single photon detectors such as SPADS, PMTs, or APDs enable the precise measurement of single photons, the quantum mechanical units of light. It thus provides access to the quantum mechanical properties of light quanta. These are specially designed detectors capable of detecting and counting individual photons. As soon as a photon hits the detector, it generates an electrical signal which is registered. The detected photons are counted and analyzed using ADCs or TDCs to obtain information about the light intensity, photon number, and other properties of the light. This enables the measurement of light in the form of individual light quanta (photons).


  • High sensitivity in detecting photons and light quanta.


  • Limited spatial resolution.
  • Limited to the measurement of optical quantum phenomena.

Application areas: spectroscopy, quantum communication and secure data transmission, quantum computing, quantum-based imaging, e.g. confocal microscopy and fluorescence imaging, bioluminescence imaging (BLI).

Photon-based detectors include e.g. SPADS, PMTs, or APDs. The figure shows an InGaAs APD receiver. This hybrid receiver features an InGaAs avalanche photodiode (InGaAs APD) and a preamplifier. The hybrid concept with an amplifier and photodetector in the same hermetically sealed TO-8 package enables low noise detection and reduces parasitic capacitance. Image by courtesy of Excelitas Technologies.