Focusing and imaging of a polarization-controlled bifocal metalens

Metalenses are a kind of flat optical device, which consist of an array of nanoantennas with subwavelength thickness that manipulates the incoming light wavefront in a precisely tailorable manner. In this work, we proposed a bifocal metalens that can realize switchable multiplane imaging, controlled by changing the polarization state of an incident light. The polarization-dependent metalens was designed and fabricated by arranging polysilicon nanobeam unit elements. We simulated and experimentally characterized the focus performance of the bifocal metalens. Under the light incidence with left-handed circular polarization, the focal length is 250 mu m. By changing the polarization state to right-handed circular polarization, the focal length is tuned to 200 mu m. Experimental results and numerical simulations are in good agreement. Moreover, when a linear polarization light is used, two focal spots will appear at the same time. Such a bifocal metalens is suitable for multiplane imaging applications. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

A bifocal metalens capable of switchable multiplane imaging was designed and fabricated, controlled by changing the polarization state of incident light. The focus performance was simulated and experimentally characterized, showing good agreement between experimental results and numerical simulations. The metalens is suitable for multiplane imaging applications with the capability to produce two focal spots simultaneously using linear polarization light.