A van der Waals Moiré Bilayer Photonic Crystal Cavity

Enhancing light–matter interactions with photonic structures is critical in classical and quantum nanophotonics. Recently, Moiré twisted bilayer optical materials have been proposed as a promising means toward a tunable platform for nanophotonic devices. However, the realization of Moiré photonic crystal (PhC) cavities has been challenging, due to a lack of advanced nanofabrication techniques and availability of stand-alone transparent membranes. Here, we leverage the properties of the van der Waals material hexagonal boron nitride to realize Moiré bilayer PhC cavities. We design and fabricate a range of devices with controllable twist angles, with flatband modes in the visible spectral range (∼450 nm). Optical characterization confirms the presence of spatially periodic cavity modes originating from the engineered dispersion relation (flatband). Our findings present a major step toward harnessing a two-dimensional van der Waals material for the next generation of on chip, twisted nanophotonic systems.