KETEK's SiPM data sheets detail key performance parameters of their silicon photomultipliers - a key parameter is Photon Detection Efficiency (PDE) which is explained in more detail below.
PDE is defined as the number of photon-discharged microcells divided by the number of incident photons. For SiPMs the PDE value depends on two parameters, the applied overvoltage or overbias (voltage above breakdown) and the wavelength of the incoming photon.
|PDE(λ, V) = QE (λ) • ε (V) • GE|
|QE = Quantum Efficiency||ε = Geiger Efficiency||GE = Geometric Efficiency||λ = Wavelength|
|V = Bias Voltage|
The Geiger efficiency increases with increasing overvoltage until it reaches its maximum, i.e. saturation, level. This plot shows the PDE at increasing overvoltage for the PM3315-WB and PM3325-WB at 420 nm. Bear in mind that Dark Count Rate and Gain also increase with increasing overvoltage so it should not be assumed that higher overvoltage = higher PDE = higher SNR!
Wavelength also affects the PDE due to the absorption characteristics of silicon at different wavelengths. KETEK's SiPMs are optimised for blue light making them ideally suited to applications utilising scintillator materials such as LSO, LYSO, NaI:Tl, CsI, GSO, Anthracen, etc. This plot shows PDE vs. wavelength at 5V overvoltage with peak sensitivity at 420 nm. Stated PDE values exclude noise effects such as dark counts, crosstalk or afterpulsing.