Asymmetric Focusing Metasurfaces with High-Q Factor and Strong Sidelobe Suppression

Optical diodes equipped with asymmetric transmission properties are essential for logic gate design in advanced optical computing chips. However, a fundamental bottleneck in asymmetric systems is the need to balance multidimensional performance, such as simultaneously meeting the collaborative control requirements of quality factor and sidelobe influence, which limits their application in integrated photonics. To overcome this challenge, we develop a composite mechanism for achieving high-performance asymmetric focusing and design a bilayer metasurface by incorporating subtle periodic perturbations within the silicon nanobars. Numerical results demonstrate strong asymmetric focusing with a Q factor exceeding 8000, along with a focal point that exhibits perfect sidelobe immunity. Furthermore, the designed bilayer metasurface exhibits strong robustness, maintaining its performance despite disturbances. This work offers a novel pathway for designing asymmetric elements for precision on-chip applications.