宽带消色差红外光学超构透镜研究进展（特邀）

超构透镜是由亚波长散射单元结构排列而成的具有聚焦功能的平面二维超构表面。超构表面能够在亚波长尺度上操控光场的振幅、相位、色散和偏振态，是近年来迅速发展起来的新型光场调控载体。亚波长共振纳米结构使得高阶衍射被抑制，入射光场可以完美地被调制到设计的衍射级次上，从而确保了超构表面器件具有高的光子调控效率。同时，超构单元在设计上的灵活性及其特定的电磁响应使得超构表面可以实现对光场多个维度的定制化操控。不同于传统光学透镜依赖光传播的相位累积效应，宽带消色差超构透镜通过对光场相位和相位色散的同时独立调控解决了传统通过级联多个透镜修正色差造成的光学系统复杂和体积庞大限制，为发展小型化片上集成光学提供了全新的思路。文中围绕超构透镜的相关研究，首先介绍了超构表面调控光场振幅、相位和偏振态的基本原理，在此基础上，重点回顾了近年来关于超透镜的研究发展，包括通过单一参量调控的单波长超透镜的实现，以及通过对光场偏振、相位及相位色散的多参量联合调控的多功能宽带消色差超构透镜的发展现状，最后讨论其进一步发展的可能挑战与应用前景。

Research progress of broadband achromatic infrared metalens (Invited)

Metalenses are two-dimensional metasurfaces composed of sub-wavelength scatters with planar configuration and light focusing function. They can manipulate the amplitude, phase, dispersion and polarization of the light field at sub-wavelength spatial resolution, and develop rapidly in recent years. The subwavelength resonant nanostructure suppresses the high-order diffraction, and the incident light can be perfectly modulated to the predesigned diffraction order, thus ensuring the high efficiency of the metadevice for manipulating the photons. Besides, the design flexibility and specific electromagnetic response of the meta-unit enable metasurfaces to achieve customized control of the multiple dimensions of the light field. In contrast to the traditional refraction lens relying on the phase accumulation effect, the broadband achromatic metalens resolves the complex and bulky limitations of the traditional optical system caused by cascading multiple lenses to correct the chromatic aberration by independently and simultaneously manipulating the phase and phase dispersion of the optical field. It provides a promising way for the miniaturization of on-chip integrated photonics. Focusing on the progress of metalens, this review discussed the basic principles of metasurface on engineering the amplitude, phase and polarization state of the light firstly. Then the development of metalens in recent years was focused on, including the realization of single-wavelength metalens and the development of multi-functional broadband achromatic metalenses through manipulating the multiple parameters (polarization, phase and phase dispersion). Finally, the potential challenges and application prospects for further developing the metalenses were discussed.