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.