Metasurface Optics for On-Demand Polarization Transformations Along the Optical Path

Abstract

Polarization plays a key role in science; hence its versatile manipulation is crucial. Existing polarization optics, however, can only manipulate polarization in a single transverse plane. Here, we demonstrate a new class of polarizers and waveplates, based on metasurfaces, that can impart an arbitrarily chosen polarization response along the propagation direction, regardless of the incident polarization. The underlying mechanism relies on transforming an incident waveform into an ensemble of pencil-like beams with different polarization states that beat along the optical axis thereby changing the resulting polarization at-will, locally, as light propagates. Remarkably, using form birefringent metasurfaces combined with matrix-based holography enable the desired propagation-dependent polarization response to be enacted without a priori knowledge of the incident polarization—a behavior that would require three polarization sensitive holograms if implemented otherwise. Our work expands the use of polarization in the design of multi-functional metasurfaces and may find application in tunable structured light, optically switchable devices, and versatile light-matter interactions.