Fig. 1: Cavity setup.
a Illustration of a non-perfectly reflecting Fabry-Pérot cavity hosting a 2D crystal. b For the mathematical description, the cavity-matter system is contained in an isotropic, cubic quantization box with sides of length L. In the out-of-plane (z)-direction the cavity and material have a fixed length scale, i.e., the mirrors are at a distance Lc and the material has a thickness d and it is placed in the center of the cavity. To make the quantization procedure simple we choose a cavity, where the in-plane length scale coincides with the quantization length, i.e., L∥ = L. Panel (b) also shows a sketch of the out-of-plane dependence for the relevant fundamental mode function M(z) of the photonic field and for the matter momentum matrix element p(z).
