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 needs to balance the multidimensional performance, such as meeting the collaborative control requirements of quality factor and sidelobe influence simultaneously, which limits the application in integrated photonics. To overcome this challenge, we develop a composite mechanism for achieving high-performance asymmetric focusing, and design a bilayer metasurfaces by incorporating subtle periodic perturbations within the silicon nanobars. Numerical results demonstrate strong asymmetric focusing with a Q-factor exceeding 8000, along with it’s a focal point that exhibits perfect sidelobe immunity effect. Furthermore, the designed bilayer metasurfaces exhibit strong robustness, remaining its performance despite disturbances. This work offers a novel pathway for designing asymmetric element in precision on-chip applications.