What we actually measure
The reflectance spectrum R(E)is the fraction of light bounced back from the stack as a function of photon energy. It is the simulator's headline output — the curve you see on the right.
What you read off it
- Cavity dips: sharp valleys where light gets stuck inside the cavity at one of its modes (see Fabry-Pérot).
- Excitonic features: extra structure where the CrSBr exciton absorbs.
- Anti-crossing:when a cavity mode and the exciton meet, both dips repel each other instead of crossing — that's the polariton signature.
How it's computed
Behind every value of R there is a TMM call: a per-layer refractive index is built from the spin pattern, the matrices are cascaded, and |r|² is read off. Walk the energy axis and you get the curve.
Key takeaways
- Dip = light got trapped (cavity) or absorbed (exciton).
- Anti-crossing = both at once → polariton.