All-dielectric high-Q dynamically tunable transmissive metasurfaces

TL;DR

This paper introduces all-dielectric active metasurfaces capable of dynamically controlling transmitted light wavefronts in the near-infrared, with high-Q resonances enabling fast thermo-optic beam switching and steering.

Contribution

It presents the design of all-dielectric transmissive metasurfaces with high-Q resonances and realistic interconnects for dynamic wavefront manipulation, including beam switching and steering.

Findings

High-Q resonances with Q-factors up to 9800 achieved in transmission.

Thermo-optic switching times as low as 7.3 microseconds.

Dynamic beam steering demonstrated using high- and lower-Q modes.

Abstract

Active metasurfaces, which are arrays of actively tunable resonant elements, can dynamically control the wavefront of the scattered light at a subwavelength scale. To date, most active metasurfaces that enable dynamic wavefront shaping operate in reflection. On the other hand, active metasurfaces operating in transmission are of considerable interest as they can readily be integrated with chip-scale light sources, yielding ultra-compact wavefront shaping devices. Here, we report designs for all-dielectric low-loss active metasurfaces which can dynamically manipulate the transmitted light wavefront in the near-infrared wavelength range. Our active metasurfaces feature an array of amorphous silicon (a-Si) pillars on a silica substate, which support resonances with quality factors (Q-factors) as high as 9800, as well as other lower-Q resonances. First, we demonstrate that high-Q resonance dips observed in transmission can be transformed into a transmission resonance peak by positioning a-Si pillar resonators at a prescribed distance from a crystalline Si substrate, defined by a silica spacer layer. Next, we report the design of metasurface geometry with realistic interconnect architectures that enable thermo-optic dynamic beam switching with switching times as low as 7.3 {\mu}s. Beam switching is observed for refractive index differences between neighboring metasurface elements as low as 0.0026. Finally, we demonstrate that metasurface structures with both high-Q and lower-Q modes and realistic interconnect architectures can be used for dynamic beam steering.