Hybrid Dispersion Engineering based on Chiral Metamirror

Dispersion is one of the key performances of optical systems. As a man-made device, metasurface is a notable alternative for dispersion manipulation and has been developed vigorously in recent years. However, the currently reported dispersion manipulation principle of meta-atoms only relies on controlling the propagation phase in the operation frequency band or several working wavelengths. In this paper, the chirality-assisted phase is introduced as an additional degree of freedom to engineer the dispersion characteristics of the meta-atom, and the strategy is theoretically demonstrated. The dispersion characteristic of the chiral meta-atom working in a reflective manner is discussed in detail within the working bandwidth. Then, two hybrid dispersion-engineered metamirrors (HDEMs) are proposed and constructed to demonstrate versatile dispersion manipulation in the working frequency band, including achromatic focusing for the lower half band and hyper dispersive focusing for the upper half band, and hyper dispersive focusing and abnormal dispersive focusing in the lower and upper half band, respectively. Both full-wave simulation and measured performances verify the validity and flexibility of the proposed strategy. This work exploits a new degree of freedom for dispersion manipulation, providing a new approach for dispersion-engineered metasurfaces design.