Generating Circularly Polarized Light Using Hybrid Near‐Zero and High‐Index Materials

Near‐zero‐refractive index materials display unique optical properties such as perfect transmission through distorted waveguides, cloaking, and inhibited diffraction. Compared to conventional media, they can fundamentally behave differently to light impinging from air owing to the phenomenon of total external reflection, which excites evanescent waves. Here, we introduce a strategy for generating circularly polarized light using evanescent wave‐based linear‐to‐circular polarization conversion. Practically realizable device designs are presented using hybrid structures of near‐zero index and high index materials in a flat‐optics geometry without the need for prism coupling or sub‐wavelength air gaps. Our results predict generation of circularly polarized light in both reflection and transmission configurations based on naturally available epsilon‐near‐zero materials and illustrate the role of loss in limiting performance. Although the operation wavelength is limited to the epsilon‐near‐zero region, the concept can be implemented from the terahertz to optical domains using tunable epsilon‐near‐zero materials.