High Transmittance and Broadband Group Delay Metasurface Element in Ka Band

On account of the tremendous phase dispersion of the metasurface elements, most of the devices based on the metasurface have distinct large chromatic aberration. Hence, achromatism has become a research hotspot in recent years. Most of the previous achromatic principles are considered from the perspective of phase compensation. In this paper, we use the group delay principle to elliminate chromatic aberration. The group delay method is easier to understand and can achieve better performance than the phase compensation method. We propose a kind of metasurface cell with different group delay based on the group delay principle and make them continuous by polynomial fitting method. This method improves the flexibility and reduces the complexity when designing achromatic focusing lens or beam deflection gradient metasurface.