Angular selection based on photonic crystals as the pseudo-local effective medium

Precise control over the angular response of light is essential for advanced photonic devices. Here, we develop a constitutive-parameters-based framework for customizable angular selection. We introduce a pseudo-local effective medium theory, leveraging Brillouin zone folding in photonic crystal supercells, to effectively realize the required parameters for a designated incident crystal face. At the operating frequency, simulations and microwave experiments demonstrate that the designed photonic crystal achieves sharp angular selection from near-total transmission (97%) to near-perfect reflection within an angular transition bandwidth of ∼3°. Additionally, by integrating a hyperbolic medium with an anisotropic medium, we realize in simulation an angular bandpass filter centered at 30° with a near 1° full width at half-maximum. This work provides a quantitative design methodology for angular-selective photonic crystals and metamaterials, paving the way for applications such as antenna sidelobe suppression, solar energy harvesting, and privacy displays.