Photon Detection Efficiency Calculator (SiPM)

Created by Dominik Czernia, PhD candidate
Reviewed by Bogna Szyk and Jack Bowater
Last updated: Feb 15, 2022

The photon detection efficiency calculator is designed to minimize the time spent on laborious calculations concerning Silicon Photomultipliers (SiPM). SiPMs are novel silicon detectors that are capable of detecting faint and fast light signals, even at a single photon level. Because of their high gain and quick response, they may find future application in medical imaging, e.g., Positron Emission Tomography (PET) or Single-Photon Emission Computed Tomography (SPECT). SiPMs are also compact and compatible with magnetic resonance devices.

Photon detection efficiency formula

The photon detection efficiency PDE is a quantity that measures the sensitivity of SiPMs. You can easily calculate it from the responsivity, R, of the sensor - with responsivity being the average photocurrent produced per unit of optical power. To make the conversion from R to PDE, you can use the following photon detection efficiency formula:

PDE = R * h * c / [e * λ * G * (1 + P_XT) * (1 + P_AP)],


  • PDE is the photon detection efficiency
  • R is the responsivity, expressed in amps per Watt A/W
  • h = 6.626 * 10⁻³⁴ m²*kg/s is Planck's constant
  • c = 2.998 * 10⁸ m/s is the speed of light
  • e = 1.602 * 10⁻¹⁹ C is elementary charge
  • λ is the wavelength of the incident light
  • G is the gain, i.e., the amount of charge created for each detected photon
  • P_XT is the crosstalk probability
  • P_AP is the afterpulsing probability

To accurately determine PDE, you should always take into account contributions due to optical crosstalk and afterpulsing. The former occurs when a single incident photon generates signals equivalent to two or more photons. The latter happens when some carriers become trapped in defects in the silicon. After some time, up to several nanoseconds, they are released, creating an additional signal. You can determine the probability of both phenomena separately by taking the appropriate measurements.

Photon detection efficiency calculator - an example

This photon detection efficiency calculator is straightforward to use and will calculate any missing variable if all of the others are provided. Simply, enter any five quantities, and the sixth will be automatically estimated. For example, let's find out what the PDE of a SiPM with the following parameters will be:

  • gain G = 1,000,000
  • crosstalk probability P_XT = 20 %
  • afterpulsing probability P_AP = 4 %

Let the incident light's wavelength be λ = 420 nm, and the responsivity R = 150,000. What is the photon detection efficiency? Fill in appropriate fields, and you'll find that PDE = 35.48 %. Isn't that simple with the photon detection efficiency calculator?

Are you interested in electronics? Check out our other exciting calculators! Visit the Shockley diode calculator to analyze the electrical properties of a real diode or the drift velocity calculator to find out how fast electricity travels.

Dominik Czernia, PhD candidate
Gain (G)
Afterpulsing probability
Crosstalk probability
Wavelength (λ)
Responsivity (R)
Photon Detection Efficiency (PDE)
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