从超振荡透镜到超临界透镜:超越衍射极限的光场调制

From super-oscillatory lens to super-critical lens:surpassing the diffraction limit via light field modulation

以超振荡透镜和超临界透镜为典型代表的平面超透镜是一种利用光场调控方式实现远场超衍射极限聚焦和成像的光学元件。通过精密调控各衍射结构单元之间的干涉效应,可以在焦平面上局部区域内获得高于系统最高空间频率的电场振荡,从而实现对衍射焦斑横向和轴向尺寸的可控调节。与传统的光学透镜相比,平面超透镜具有聚焦能力强,结构紧凑,设计自由度大,利于集成等优点。因其远场超衍射极限的光场调控能力,受到衍射光学和纳米光子学领域人员的广泛关注和研究。本文介绍了平面超衍射极限透镜光场调控的原理和设计方法。对超振荡透镜和超临界透镜的研究现状及其在远场光学超分辨成像领域的应用进行了分析和讨论,最后对该领域面临的问题及其拓展方向作了展望。

Super-oscillatory lens（SOL） and super-critical lens（SCL） are the typical representatives of planar metalens which could achieve sub-diffractive focusing and imaging in far field by means of light field modulation. Through precisely modulating the interference effect of each diffractive unit, the electromagnetic wave could be oscillated faster than its maximum frequency components in a certain region of the target plane, and then the focal spot size is controllable in lateral and longitudinal directions. Compared with the traditional optical lens, the planar metalens is much more attractive in the fields of diffractive optics and nanophotonics due to its distinct advantages of powerful focusing capabilities, compact configuration, higher design freedom and the integratable properties, etc. In this review, we briefly introduce the field modulation mechanism and design principle of planar metalens. The research advances of the super-oscillatory lens and super-critical lens, as well as their applications in far-field label-free super-resolution imaging, are discussed in detail. In addition, a perspective about the future outlook of planar metalens is summarized. Since the planar metalens has powerful capability in manipulating the light field, the rapid development in various applications would be gradually realized in the near future.