  A theoretical variation between the two distinct light-matter coupling
regimes, namely weak and strong coupling, becomes uniquely feasible in open
optical Fabry-P\'erot microcavities with low mode volume, as discussed here. In
combination with monolayers of transition-metal dichalcogenides (TMDCs) such as
WS2, which exhibits a large exciton oscillator strength and binding energy, the
room-temperature observation of hybrid bosonic quasiparticles, referred to as
exciton-polaritons and characterized by a Rabi splitting, comes into reach. In
this context, our simulations using the transfer-matrix method show how to
tailor and alter the coupling strength actively by varying the relative field
strength at the excitons' position - exploiting a tunable cavity length, a
transparent PMMA spacer layer and angle-dependencies of optical resonances.
Continuously tunable coupling for future experiments is hereby proposed,
capable of real-time adjustable Rabi splitting as well as switching between the
two coupling regimes. Being nearly independent of the chosen material, the
suggested structure could also be used in the context of light-matter-coupling
experiments with quantum dots, molecules or quantum wells. While the adjustable
polariton energy levels could be utilized for polariton-chemistry or optical
sensing, cavities that allow working at the exceptional point promise the
exploration of topological properties of that point.
