Electrically tunable liquid-crystal metasurfaces with patterned birefringence and dichroism

TL;DR

This paper presents electrically tunable liquid-crystal metasurfaces with patterned birefringence and dichroism, enabling precise control of light's polarization and diffraction properties through integrated dye molecules and electric fields.

Contribution

It introduces a novel class of liquid-crystal metasurfaces with patterned birefringence and dichroism, modeled using non-unitary Jones matrices and validated by polarimetric measurements.

Findings

Dichroic dye molecules effectively couple birefringence and dichroism effects.

Diffraction efficiency can be tuned by electric fields through birefringence and dichroism.

The study enhances understanding of light propagation in anisotropic materials with dichroism.

Abstract

Light propagation through artificially patterned anisotropic materials, such as dielectric metasurfaces, enables precise control of the spatio-vectorial properties of optical fields using highly transparent, thin, and flat optical elements. Liquid-crystal cells are a common realization of such devices. Optical losses are typically assumed to be polarization-independent and are therefore often overlooked in modeling these systems. In this work, we introduce electrically tunable liquid-crystal metasurfaces with patterned birefringence and dichroism, achieved by incorporating dichroic dye molecules into the liquid-crystal mixture. These dye molecules align with the liquid crystal, effectively coupling birefringence and dichroism effects. The behavior of these metasurfaces is described using non-unitary Jones matrices, validated through polarimetric measurements. In the case of devices that are patterned to form polarization gratings, we also characterize the diffraction efficiency as a function of the dichroism and birefringence parameters, which can be tuned jointly by applying an electric field across the cell. This study not only introduces a new class of optical components but also deepens our understanding of light propagation through anisotropic materials, where dichroism can naturally arise from bulk material properties or from reflection and transmission laws at their interfaces.