Device Platform for Electrically Reconfigurable Dielectric Metasurfaces

TL;DR

This paper presents a novel solid-state device platform for electrically reconfigurable dielectric metasurfaces, enabling independent control of optical antenna elements for dynamic wavefront manipulation.

Contribution

The work introduces a new heterostructure design and fabrication process for tunable metasurface elements with large phase modulation capabilities.

Findings

Resonant wavelength blue shifts by 200nm during carrier injection.

Achieves nearly π phase shift in a metasurface array.

Demonstrates independent electrical control of resonant elements.

Abstract

Achieving an electrically tunable phased array optical antenna surface has been a principal challenge in the field of metasurfaces. In this letter, we demonstrate a device platform for achieving reconfigurable control over the resonant wavelength of a subwavelength optical antenna through free-carrier injection. We engineer and grow, using molecular beam epitaxy, a heterostructure of In1-xAlxAs/InAs/AlyGa1-ySb layers designed to achieve large amplitude and phase modulation of light by maximizing the refractive index change in regions of resonant field enhancement The p-i-n layers are grown on a heavily doped n-InAs layer which forms a reflecting substrate to confine the Mie resonances within the nanowires of the index tunable layers. We outline the fabrication process developed to form such tunable metasurface elements using a four-step projection lithography process and a self-aligned vertical dry etch. We experimentally demonstrate the operation of an electrically reconfigurable optical antenna element where the resonant wavelength blue shifts by 200nm only during carrier-injection. We extrapolate the experimentally measured InAs refractive index shifts to show we can achieve nearly {\pi} phase shift in a metasurface array. This solid-state device platform enables us to contact each resonant element independently to form a truly reconfigurable Fourier optical element with the promise of arbitrary control of the electromagnetic wavefront at the subwavelength scale.