Gate-Tunable Transmissive Metasurfaces for Beam Steering

Our latest work, “Nanoscale Transmissive Gate-Tunable Conducting Oxide Metagrating for Beam-Steering Modulation,” has been published online in ACS Applied Nano Materials.

Conventional optical components typically have fixed functions once they are fabricated. A grating, for example, redirects light into predetermined directions, and changing those directions often requires mechanical motion, structural modification, or additional optical components. What if light could instead be controlled electronically—simply by changing an applied voltage?

In this work, we developed a nanoscale transmissive gate-tunable conducting-oxide metagrating based on a metal–oxide–semiconductor (MOS) architecture incorporating indium zinc oxide (IZO) as the active material. Applying a gate voltage changes the carrier concentration in the IZO layer, which in turn modifies its optical properties and enables voltage-dependent control over the amplitude and phase of transmitted light.

From Applied Voltages to Beam Control

A central question of this work goes beyond tuning an individual nanostructure: If different nanoscale elements across a metasurface can be assigned different voltages, can these electrical degrees of freedom be optimized to control the overall optical wavefront?

To explore this concept, we combined the tunable MOS/IZO metasurface with a gradient-based inverse-design framework. Instead of relying on a simple predefined voltage pattern, the optimization algorithm searches for multilevel voltage distributions that make better use of the available amplitude and phase responses of individual meta-atoms, directing more transmitted optical power toward the desired diffraction order.

Numerical optimization predicts relative +1st-order diffraction efficiencies of approximately 14% across different steering angles, with full-wave electromagnetic simulations yielding efficiencies close to 10%. These results demonstrate how inverse design can exploit the available optical degrees of freedom even when the phase-tuning range of an individual tunable meta-atom is limited.

From Numerical Design to Experimental Validation

We further fabricated a 40-μm-scale binary gate-tunable metagrating as an experimental proof-of-concept device. The experiment demonstrated voltage-dependent transmissive diffraction, with a measured deflection angle of 51.68°, in close agreement with the theoretically predicted value of 50.81°. This result experimentally validates the underlying mechanism for electrically controlling diffraction in the transmissive MOS/IZO platform.

Importantly, the present experiment demonstrates a simpler binary-voltage device, whereas the inverse-designed multilevel metagratings are demonstrated numerically. Rather than representing a complete dynamic beam-scanning system, this work establishes a foundation connecting carrier modulation, nanoscale optical response, voltage-distribution optimization, and transmissive beam control.

Toward Electrically Programmable Meta-Optics

An important direction of this work is to extend the design freedom of metasurfaces beyond their physical nanostructures to the electrical voltages applied across the device.

In this picture, the optical response of a metasurface does not necessarily have to be completely fixed during fabrication. Instead, electronic control may provide an additional layer of programmability after fabrication. With future improvements in gate-dielectric reliability, independently addressable multielectrode circuitry, and meta-atom efficiency, this platform could provide a pathway toward programmable beam steering, LiDAR, dynamic wavefront control, and integrated photonic systems.

Publication

W.-C. Tsai, Y.-H. Huang, Y.-H. Xie, and Y.-W. Huang*, “Nanoscale Transmissive Gate-Tunable Conducting Oxide Metagrating for Beam-Steering Modulation,” ACS Applied Nano Materials 9(31), 14707–14717 (2026) (2026) - LINK & PDF

Featured on the journal cover - LINK