Complex-amplitude metalens with extended depth of focus and enhanced focal uniformity

Abstract

Deep depth of focus (DoF) metalenses have wide application prospects in the fields of security inspection, biological observation, and 3D imaging. However, prevailing design approaches have inherent defects such as numerical aperture (NA) constraints and poor focal uniformity. To conquer these limitations, a complex-amplitude (CA) deep DoF metalens is demonstrated in the microwave region, enabled by the marriage of a novel 3D CA retrieval method and the C-shaped meta-atoms. An extended DoF of 6.9λ can be simulated, corresponding to the NA range from 0.8725 to 0.4582. Meanwhile, the lateral focal spot is uniformly distributed longitudinally, with the variance value of 21.03 in the focal spot diameter. The proposed retrieval method can provide an optimized design strategy for the deep DoF metalens, ensuring the DoF accuracy and the focal uniformity. The numerical comparison results prove the validity and superiority of this method.