Design of self-collimated photonic crystals based on hexagonal boron nitride in the visible region

Two-dimensional (2D) hexagonal boron nitride (hBN) can serve as an ultrabright and photostable single-photon emitter at room temperature, making it a promising candidate for integrated optical devices based on the hBN material platform. In this study, we proposed a 2D hBN photonic crystal (PhC) structure that exhibits self-collimation behavior within a normalized frequency range of 0.57-0.66 (a/λ), corresponding to 589-682 nm in wavelength. Here, we used C4-symmetric hBN rods with attached short connecting sticks to enable the PhC to function as a freestanding device. The corresponding band diagrams and equal-frequency contours (EFCs) were calculated using the plane-wave expansion (PWE) method, and a contour map was analyzed to verify the self-collimation effect. The results demonstrate the self-collimation capability of a point source within the proposed hBN PhC across the visible spectrum. This design paves the way for achieving self-collimating focusing in future nanophotonic integrated chips.