Micro Photon Devices standard products are single-photon counting and timing modules, although recently MPD has also started to develop and manufacture electronic instrumentation, typically compendium to the usage of our photon detector modules.

Besides our undisputable detection technologies and capabilities, we have the electronic expertise, product engineering and production experiences to enhance and accelerate customer OEM designs.

MPD in-depth know-how of SPAD device fabrication and gated/free-running active quenching electronics has led the company to develop and market a comprehensive family of Single Photon Avalanche Diodes (SPADs). These are self-contained modules that meet the low light level analytical detection demands, down to the single photon level, with high photon detection efficiency (PDE) and low internal “noise” (i.e. the dark-count rate (DCR) and afterpulsing) for application such as confocal microscopy, fluorescence, luminescence and TCSPC.

"The SPAD is a reverse biased p-n junction, working with an applied voltage well above the breakdown voltage. This implies that the electric field in the depleted region is so high to be able to trigger an avalanche multiplication process and to self-sustain a current flow after the generation of only one electron-hole pair, e.g. due to the absorption of a single photon.

Once a photon an avalanche is generated, the current swiftly rises with nanosecond or sub-nanosecond rise time to a macroscopic steady level in the milliampere range, which can be easily discriminated. If the primary carrier is photogenerated, the leading edge of the avalanche pulse marks the arrival time of the detected photon. After the avalanche is triggered, the current keeps flowing until the avalanche is quenched by lowering the bias voltage down to breakdown voltage or below. The bias voltage is then restored in order to detect another photon. This operation requires a suitable circuit that is usually referred to as a quenching circuit. Because of the similarity with the behaviour of Geiger-Muller detectors, SPADs are referred to work in “Geiger mode”.

As in any other sensors, SPADs have their own internal noise which is due to thermal generation effects that produce current pulses even in the absence of illumination, called dark counts (DC). The rate of these dark counts (DCR) increases with the temperature and also with the overvoltage. A secondary noise source, called afterpulsing, may strongly enhance the total dark count rate. This is caused by carriers trapped during the avalanche formation and which are subsequently released. These carriers are accelerated by the intense electric field across the junction and can retrigger another avalanche, generating afterpulses correlated with a previous avalanche pulse."

MPD SPADs offer market-leading photon detection performances:

  • Extremely Low Timing Resolution, down to few tenth of picoseconds
  • High Photon Detection Efficiency, up to 60%
  • Low dark counts, down to 1cps
  • Low afterpulsing, down to 0.1%
  • Uniformity of characteristics over the detector active area

Our photon detectors cover the electromagnetic spectrum from the near infrared all the way up to the near ultraviolet.


MPD’s SPADs perform well in a variety of cutting-edge applications including:

  • Particle Sizing
  • Confocal Microscopy
  • Ultra-Sensitive Fluorescence
  • Luminescence
  • Time-correlated single photon counting
  • Single Molecule Detection
  • Astronomic Observations & Adaptive Optics
  • Optical Range Finding, LIDAR & LADAR
  • Quantum Cryptography & Quantum Optics
  • Single-photon source characterization
  • Optical testing of integrated circuits


MPD’s entire product range is designed and built to be fully RoHS-compliant.