Chen Li, Hao Yuan, Zhao Lin, Wu Ruihuan, Liu Yue, Wei Zhongchao, Xu Ning, Li Zhaotang, Liu Hongzhan
Opt Express. 2021 Mar 15;29(6):9332-9345. doi: 10.1364/OE.420003.
Optical metasurfaces exhibit unprecedented ability in light field control due to their ability to locally change the phase, amplitude, and polarization of transmitted or reflected light. We propose a multifunctional metalens with dual working modes based on bilayer geometric phase elements consisting of low-loss phase change materials (SbSe) and amorphous silicon (a-Si). In transmission mode, by changing the crystalline state of the SbSe scatterer, a bifocal metalens with an arbitrary intensity ratio at the telecommunication C-band is realized, and the total focusing efficiency of the bifocal metalens is as high as 78%. Also, at the resonance wavelength of the amorphous SbSe scatterer, the scatterer can be regarded as a half-wave plate in reflection mode. The multifunctional metalens can reversely converge incident light into a focal point with a focusing efficiency of up to 30%. The high focusing efficiency, dynamic reconfigurability, and dual working modes of the multifunctional metalens contribute to polarization state detection, optical imaging, and optical data storage. In addition, the bilayer geometric phase elements can be easily extended to multilayer, which significantly improves the capability of manipulating the incident light field.
光学超表面由于能够局部改变透射或反射光的相位、幅度和偏振，在光场控制方面展现出前所未有的能力。我们基于由低损耗相变材料（SbSe）和非晶硅（a-Si）组成的双层几何相位元件，提出了一种具有双工作模式的多功能金属透镜。在透射模式下，通过改变SbSe散射体的晶态，实现了在电信C波段具有任意强度比的双焦金属透镜，且双焦金属透镜的总聚焦效率高达78%。此外，在非晶态SbSe散射体的共振波长处，该散射体在反射模式下可被视为一个半波片。这种多功能金属透镜能够将入射光反向聚焦到一个焦点上，聚焦效率高达30%。多功能金属透镜的高聚焦效率、动态可重构性和双工作模式有助于偏振态检测、光学成像和光学数据存储。此外，双层几何相位元件可以很容易地扩展到多层，这显著提高了操纵入射光场的能力。
