Metasurfaces, nanophotonic arrays of subwavelength phase shifting elements, hold promise for the miniaturization of a variety of bulk optical elements. Owing to the flexibility with which their constituent elements may be engineered, metasurfaces allow for point-to-point polarization control on a subwavelength scale. Metasurfaces, then, represent an exciting new platform for polarization optics.
A single metasurface may combine many different polarization-dependent functionalities that would ordinarily be spread out over many optical elements. We describe how, through relatively simple optimization methods, a metasurface producing arbitrarily specified polarization states can be designed. This functionality is equivalent to a traditional diffraction grating with individual waveplate optics on each order; here, all the necessary polarization optics can be integrated into a flat, efficient, and ultrathin metasurface optical element. Moreover, such a metasurface can be used in a reverse configuration as a parallel snapshot polarimeter with no need for additional polarization optics. We present a detailed experimental characterization of this device in the visible spectral region and a comparison of the performance of the metasurface to a commercially available rotating waveplate polarimeter.
Metasurfaces can enable compact, miniaturized sensors for polarimetry and polarization imaging. We will conclude with a perspective on these possibilities and their implications for remote sensing. Metasurface polarization optics can overcome limitations of previous diffractive/grating based polarimetry schemes are potentially of significant interest to the imaging polarimetry community.