Multifunctional all-dielectric metasurface quarter-wave plates for polarization conversion and wavefront shaping

Different from conventional optical waveplates, which suffer from limited functionalities and bulky configurations, metasurfaces provide full-range birefringence control along with unprecedented capabilities of wavefront shaping at any wavelength range of interest with properly designed anisotropic meta-atoms, thereby resulting in miniaturized planar meta-waveplates with excellent and fancy functionalities beyond the conventional counterparts. In this Letter, we design a set of dielectric metasurface quarter-wave plates (QWPs) that enable efficient circular-to-linear polarization conversion along with complete phase control over the converted linearly polarized beam under circularly polarized (CP) excitation. Capitalizing on this meta-QWP platform, we numerically demonstrate two advanced multifunctional meta-QWPs (i.e., a beam-steerer and a focusing metalens) to generate different wavefronts with homogeneous and inhomogeneous linear polarization distributions under CP excitation, mimicking the functionalities of cascaded multi-stage optical components. Owing to the compactness, flexibility, and versatility, such meta-QWPs are capable of integrating more advanced applications in polarization optics.