Electrically switchable diffractive waveplates with metasurface aligned liquid crystals.

Jeffrey Chou,Brian Kimball,Lalitha Parameswaran,Mordechai Rothschild

doi:10.1364/oe.24.024265

Abstract

Diffractive waveplates and equivalent metasurfaces provide a promising path for applications in thin film beam steering, tunable lenses, and polarization filters. However, fixed metasurfaces alone are unable to be tuned electronically. By combining metasurfaces with tunable liquid crystals, we experimentally demonstrate a single layer device capable of electrically switching a diffractive waveplate design at a measured peak diffraction efficiency of 35%, and a minimum switching voltage of 10V. Furthermore, the nano-scale metasurface aligned liquid crystals are largely independent of variations in wavelength and temperature. We also present a computational analysis of the efficiency limits of liquid crystal based diffractive waveplates, and compare this analysis to experimental measurements.

Highlights

Diffractive waveplates (DW) offer extremely high diffraction efficiencies by utilizing a liquid crystal layer only microns thick [1]
Diffractive waveplates and equivalent metasurfaces provide a promising path for applications in thin film beam steering, tunable lenses, and polarization filters
By combining metasurfaces with tunable liquid crystals, we experimentally demonstrate a single layer device capable of electrically switching a diffractive waveplate design at a measured peak diffraction efficiency of 35%, and a minimum switching voltage of 10V

Summary

Introduction

Diffractive waveplates (DW) offer extremely high diffraction efficiencies by utilizing a liquid crystal layer only microns thick [1]. Under the correct configuration, full electronic tunability may be accomplished to allow for optoelectronic, thin film beam steering, tunable lenses, beam shaping, and polarization filters [1,2,3,4,5,6,7]. Axial wave plates (AWP) have been developed to control beam shapes and generate highly ordered “doughnut” beams for applications in imaging, spectral filtering, and optical tweezers [5,8]. All dielectric metasurfaces have been demonstrated as highly efficiency flat lenses and polarization filters, these devices remain fixed and are unable to be tuned electronically [9,10,11]. The aim of this work is to study electrically tunable metasurface designs using liquid crystals as the enabling material

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Conclusion