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

Light in the mid-infrared (mid-IR) spans wavelengths from 3 to 8 micrometers and is important to many applications such as gas sensing and thermal imaging. Due to materials challenges, there is now 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 (10¹⁹ per cubic centimeter) film of indium tin oxide 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. Last, 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.