Achromatic flat focusing lens based on dispersion engineering of spoof surface plasmon polaritons

In this letter, we first analyze the dispersion relation for achromatic focusing and obtain the achromatic focusing conditions for discretized unit cells of flat lenses. Then, we propose to engineer the dispersion of spoof surface plasmon polaritons (SSPPs) to satisfy the achromatic focusing conditions. Metallic blades structures are utilized to achieve the linear dispersion response by tailoring the weak dispersion region of SSPPs. A broadband achromatic flat focusing lens (AFFL) is implemented with delicate combinations of the blade structures. A prototype was designed, fabricated, and measured. Both the simulated and experimental results demonstrate that the proposed AFFL can achieve achromatic focusing from 7.5 to 9.0 GHz under the normal incidence. Published by AIP Publishing.