Fundamental Limits of Ultrathin Metasurfaces

TL;DR

This paper establishes fundamental theoretical limits on the performance of non-magnetic passive ultrathin metasurfaces, showing inherent constraints on their ability to control light phase and polarization conversion efficiency.

Contribution

It provides universal bounds on transmission, reflection, and polarization conversion coefficients, revealing that full phase control without polarization change is impossible with such metasurfaces.

Findings

Transmission, reflection, and polarization coefficients are confined to limited regions of the complex plane.

Maximum polarization conversion efficiency in transmission is limited to 25%.

Full phase control without polarization change cannot be achieved.

Abstract

We present universal theoretical limits on the operation and performance of non-magnetic passive ultrathin metasurfaces. In particular, we prove that their local transmission, reflection, and polarization conversion coefficients are confined to limited regions of the complex plane. As a result, full control over the phase of the light transmitted through such metasurfaces cannot be achieved if the polarization of the light is not to be affected at the same time. We also establish fundamental limits on the maximum polarization conversion efficiency of these metasurfaces, and show that they cannot achieve more than 25% polarization conversion efficiency in transmission.