  Efficient nanophotonic devices are essential for applications in quantum
networking, optical information processing, sensing, and nonlinear optics.
Extensive research efforts have focused on integrating two-dimensional (2D)
materials into photonic structures, but this integration is often limited by
size and material quality. Here, we use hexagonal boron nitride (hBN), a
benchmark choice for encapsulating atomically thin materials, as a waveguiding
layer while simultaneously improving the optical quality of the embedded films.
When combined with photonic inverse design, it becomes a complete nanophotonic
platform to interface with optically active 2D materials. Grating couplers and
low-loss waveguides provide optical interfacing and routing, tunable cavities
provide a large exciton-photon coupling to transition metal dichalcogenides
(TMD) monolayers through Purcell enhancement, and metasurfaces enable the
efficient detection of TMD dark excitons. This work paves the way for advanced
2D-material nanophotonic structures for classical and quantum nonlinear optics.
