SiPM Photon Detection Efficiency Calculator

About SiPM photon detection efficiency

A silicon photomultiplier, or SiPM, is an array of avalanche photodiode microcells operated above breakdown voltage in Geiger mode. A photon absorbed in an active region can create an electron-hole pair that starts a self-sustaining avalanche. Each fired microcell produces a measurable pulse, and the combined array can detect very low light levels while operating at practical voltages. Photon detection efficiency, commonly abbreviated PDE, expresses the probability that an incident photon produces a registered avalanche. PDE is not identical to quantum efficiency. Quantum efficiency describes the probability that silicon absorbs a photon and creates a useful charge carrier. Avalanche trigger probability describes whether that carrier initiates a Geiger discharge. Geometric fill factor accounts for inactive structures between microcells. Their product, with other collection effects when known, estimates detector PDE. This calculator uses a smooth representative silicon wavelength response centered near 550 nm, an exponential trigger model based on overvoltage, the entered fill factor, and a modest temperature correction. It is an engineering model, not a substitute for a manufacturer's measured PDE curve. Overvoltage is bias voltage minus breakdown voltage. Increasing it generally raises avalanche probability, gain, crosstalk, afterpulsing, and dark noise. The calculator requires positive overvoltage and reports its modeled trigger probability. Breakdown voltage itself changes with temperature, so laboratory work should use the value measured or specified at the operating temperature. The simple temperature factor included here approximates sensitivity drift only; it does not replace device-specific compensation coefficients. Dark count rate measures avalanches generated without incident signal photons. Thermal carrier generation makes dark rate strongly temperature dependent, often approximately doubling over a characteristic temperature interval. The calculator applies an eight-degree doubling model to the entered reference rate. Cooling can greatly improve low-light performance, although correlated noise and readout electronics must also be considered. Optical filter efficiency is applied after detector PDE to estimate the fraction of photons upstream of the filter that become detections. Wavelength response, microcell geometry, fabrication process, recovery time, saturation, crosstalk, and afterpulsing all affect real performance. Larger microcells often provide higher fill factor and gain but reduce dynamic range because fewer cells fit in the same area. The displayed timing value is a comparative estimate derived from microcell size rather than a guaranteed resolution. Use this calculator to compare operating scenarios, then confirm a design with datasheet curves and measurements for the exact SiPM.

SiPM efficiency examples

How to use the calculator

1. Enter wavelength and operating temperature for the optical measurement.
2. Enter bias and breakdown voltages to establish positive overvoltage.
3. Add dark count rate, filter efficiency, fill factor, and microcell size.
4. Select Calculate SiPM efficiency and compare detector PDE with overall optical efficiency.

Frequently asked questions