Electro-optic modulation of coherent and incoherent mid-IR radiation in two-dimensional arrays

TL;DR

This paper introduces an electrically controlled metasurface capable of modulating both coherent and incoherent mid-infrared radiation in two dimensions, enabling dynamic beam steering and emissivity control for applications like sensing and thermal imaging.

Contribution

It presents a novel, scalable, electrically addressable metasurface using ITO for mid-IR modulation, including a perimeter-driven scheme for 2D diffraction control and thermal emissivity reconfiguration.

Findings

Achieved tunable diffraction of mid-IR light with 32 elements

Implemented a scalable perimeter-addressed driving scheme

Demonstrated reconfigurable emissivity patterns at high temperatures

Abstract

Light in the mid-infrared (mid-IR) spans wavelengths from 3-8 $\mu$m and is important to many applications such as gas sensing and thermal imaging. Due to materials challenges, there is currently a lack of mid-IR reconfigurable optical elements. Here, we present an electrically addressable metasurface for modulation of coherent and incoherent mid-IR radiation in two spatial dimensions. Our device achieves optical modulation due to the field-effect free-carrier depletion in a lightly doped ($10^{19}$ cm$^{-3}$) film of indium-tin-oxide (ITO) coupled to a gap plasmon resonator. By addressing 32 individual elements across the metasurface, we first demonstrate tunable diffraction of coherently reflected mid-IR light. Next, we introduce a scalable perimeter-addressed driving scheme for tunable diffraction in two dimensions. Finally, we demonstrate modulated emissivity with spatially reconfigurable two-dimensional patterns at elevated temperatures. This work advances the development of solid-state reflective beam-steering devices in the mid-IR and manipulation of thermally emitted incoherent radiation.