Ultrawideband chromatic aberration-free meta-mirrors

Chromatic aberration-free meta-devices (e.g., achromatic meta-devices and abnormal chromatic meta-devices) play an essential role in modern science and technology. However, current efforts suffer the issues of low efficiency, narrow operating band, and limited wavefront manipulation capability. We propose a general strategy to design chromatic aberration-free meta-devices with high-efficiency and ultrabroadband properties, which is realized by satisfying the key criteria of desirable phase dispersion and high reflection amplitudes at the target frequency interval. The phase dispersion is tuned successfully based on a multiresonant Lorentz model, and high reflection is guaranteed by the presence of the metallic ground. As proof of the concept, two microwave meta-devices are designed, fabricated, and experimentally characterized. An achromatic meta-mirror is proposed within 8 to 12 GHz, and another abnormal chromatic meta-mirror can tune the reflection angle as a linear function. Both meta-mirrors exhibit very high efficiencies (85% to 94% in the frequency band). Our findings open a door to realize chromatic aberration-free meta-devices with high efficiency and wideband properties and stimulate the realizations of chromatic aberration-free meta-devices with other functionalities or working at higher frequency.