Generalized phase profile design method for tunable devices using bilayer metasurfaces

Abstract

Tunable devices based on bilayer metasurfaces have attracted researchers’ attention in recent years for their accurate tuning abilities and high integration. In tunable devices such as tunable beam splitters and Alvarez metalenses, opposite quadratic or cubic target phase profiles are imparted on both layers, and a varying total phase profile arises through the relatively lateral displacement between the two layers. However, there is a lack of a generalized target phase profile design method to design these tunable devices. In this study, a generalized phase profile design method named Integral of Total Phase Profile Difference (ITPD) is proposed to calculate the target phase profiles of both layers. Multiple integral equations describe the relationship between the target phase profiles and the total phase profiles. Based on this method, a tunable beam splitter and an Alvarez metalens are redesigned respectively. Moreover, a new tunable device that can be converted from a beam splitter to a metalens is designed by the ITPD method. The ITPD design method is promising for designing tunable devices with arbitrary total phase profiles in dynamic or multifunctional optical systems.