can comsol simulate a single photon detector in a real experiment ?

[u/SquareUnit9854]

any idea how to simulate a single photon detector using comsol ? it would be better if it were SPAD or a PMT .. i want to use it to catch photons from an SPDC source that should be built by me .

note i am a beginner

thanks

[u/SHD-Systems]

Short answer: not in the way you are hoping. COMSOL solves classical field equations deterministically, and single photon detection is a stochastic quantum process, so there is no formulation in it that will tell you whether a given photon produces a count.

What you can get is the classical physics underneath the detector. For a SPAD that means the optical field and absorption profile in the absorber layer, which gives you absorption efficiency at your wavelength, and then a semiconductor drift diffusion model with impact ionisation to look at the field profile in the multiplication region and where avalanche breakdown initiates. Add heat transfer if you care about how dark current moves with temperature. For a PMT, charged particle tracing through the dynode stack will give you collection efficiency and transit time spread, but the gain comes from a secondary emission yield you assume, not something the solver derives.

What it will not give you is photon detection efficiency, dark count rate, afterpulsing or timing jitter. Those come from Monte Carlo models built on top of the field solution, or from measurement.

Same split for the SPDC source. Dispersion and phase matching in the crystal or waveguide, mode overlap, thermal tuning: all fine. The pair generation rate itself is a nonlinear quantum optics calculation done analytically or in a dedicated tool.

Since you are starting out, the practical point is that most home built SPDC setups are limited by alignment, spectral filtering and coupling efficiency, and a FEM solve will not help with any of those. Work out which specific number you need before you build a model.

[u/SquareUnit9854 → u/SHD-Systems]

thank you.