Optical angular transparency and broadband absorption based on photonic topological transition in black phosphorus/aluminum oxide hyperbolic metamaterial

Based on the photonic topological transition (PTT), the transmission properties of a black phosphorus/aluminum oxide multilayered hyperbolic metamaterial (HMM) are theoretically investigated in the mid-infrared region. The results demonstrate that an angular transparency window appears near the transition point of PTT, which is achieved by tailoring the topology of the HMM’s equi-frequency surface. The angular full width at half maximum of the transparency window is 2.34°, and the transmittance is higher than 99.8% at normal incidence. In addition, the operating wavelength can be flexibly tuned by adjusting the concentration of electrons. Besides, a layered cascade structure with a wide operating wavelength (1 µm) and an enhanced angular selectivity performance is proposed, which resolves the shortcoming of a single working wavelength. In addition, the spectral-selective behavior of absorption is also explained based on the PTT. These attractive properties make the black phosphorus-based HMM hold promise for potential applications in angularly selective systems and energy harvesting.