Complex-birefringent dielectric metasurfaces for arbitrary polarization-pair transformations

TL;DR

This paper introduces complex-birefringent metasurfaces capable of arbitrary polarization transformations, including quantum state modifications, by leveraging loss and tailored nanoresonator structures for advanced classical and quantum polarization control.

Contribution

It presents a novel class of metasurfaces that enable arbitrary polarization pair transformations and quantum state modifications, expanding the capabilities of flat polarization optics.

Findings

Demonstrated metasurfaces amplify small polarization differences.

Achieved arbitrary biphoton polarization transformations.

Validated theoretical design with experimental results.

Abstract

Birefringent materials or nanostructures that introduce phase differences between two linear polarizations underpin the operation of wave plates for polarization control of light. Here we develop metasurfaces realizing a distinct class of complex-birefringent wave plates, which combine polarization transformation with a judiciously tailored polarization-dependent phase retardance and amplitude filtering via diffraction. We prove that the presence of loss enables the mapping from any chosen generally non-orthogonal pair of polarizations to any other pair at the output. We establish an optimal theoretical design-framework based on pairwise nanoresonator structures and experimentally demonstrate unique properties of metasurfaces in the amplification of small polarization differences and polarization coupling with unconventional phase control. Furthermore, we reveal that these metasurfaces can perform arbitrary transformations of biphoton polarization-encoded quantum states, including the modification of the degree of entanglement. Thereby, such flat devices can facilitate novel types of multi-functional polarization optics for classical and quantum applications.