Optimal condition to probe strong coupling of two-dimensional excitons and zero-dimensional cavity modes

The light-matter interaction associated with a two-dimensional excitonic transition coupled to a zero-dimensional photonic cavity is fundamentally different from cavity-coupled localized excitations in quantum dots or color centers, which have negligible spatial extent compared to the cavity-confined mode profile. We provide a succinct expression for calculating the light-matter interaction of a two-dimensional optical transition coupled to a zero-dimensional confined cavity mode. From this expression, we found there is an optimal spatial extent of the excitonic transition that maximizes such an interaction strength due to the competition between minimizing the excitonic envelope function area and maximizing the total integrated field. We also found that at near zero exciton-cavity detuning, the direct transmission efficiency of a waveguide-integrated cavity can be severely suppressed, which suggests performing experiments using a side-coupled cavity.