Deterministic approach for integrating an emitter in a nanocavity with subwavelength light confinement

We introduce a novel light-matter interface that integrates a nanoscale buried heterostructure emitter into a dielectric bowtie cavity, co-localising the optical hotspot and the electronic wavefunction. This platform enables strong light-matter interaction through deep subwavelength confinement while remaining compatible with scalable fabrication. We show that in this regime an explicit treatment of the emitter's spatial extent is required, and that a confinement-factor approximation more accurately predicts the coupling, revealing design rules inaccessible to dipole-based metrics. For an InP/InGaAsP system, we predict coupling strengths of 0.4-0.7 meV for gap sizes of 50-10 nm, establishing the buried heterostructure-bowtie architecture as a practical route to deterministic strong coupling in solid-state nanophotonics.