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Gate-Tunable Transmissive Metasurfaces with Dual-Resonance-Enhanced Modulation
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DOI：10.1021/acsphotonics.6c00577.png)
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Abstract
En 中文
Electrically tunable metasurfaces enable dynamic control of light in ultrathin optical platforms. Most solid-state implementations rely on reflection-mode operation to achieve strong light–matter interaction, which limits their compatibility with transmissive and monolithically integrated photonic systems. In this work, we demonstrate a solid-state, electrically tunable transmissive metasurface based on a metal–oxide–semiconductor (MOS) architecture that overcomes this constraint by engineering vertical optical confinement in transmission mode. The metasurface consists of plasmonic gold nanoantennas separated from a semitransparent gold layer by an Al2O3/indium tin oxide (ITO) stack, with an additional amorphous silicon layer beneath the semitransparent metal. This vertical heterostructure forms a Fabry–Pérot cavity that couples to a gap plasmon resonance supported by the nanoantennas, enabling strong electric-field confinement within the electrically gated ITO accumulation layer while preserving forward transmission. Electrical bias drives the ITO into the epsilon-near-zero regime, producing a pronounced modulation of the transmitted intensity. The device experimentally exhibits a peak transmittance of 24.4% and a relative transmission modulation of 9.4% at a wavelength of 1494 nm under a low driving voltage of under ±3.5 V bias, in good agreement with numerical simulations. High-speed measurements reveal a −3 dB modulation bandwidth of 7.7 MHz, primarily limited by device capacitance. The fully solid-state, CMOS-compatible architecture provides a compact platform for high-speed transmissive optical modulation, with potential applications in beam steering and free-space optical communications.
Keywords:
Gold
Layers
Metasurfaces
Nanodevices
Optical properties
Gate-tunable metasurface
Active transmissive metasurface
Free-space transmissive amplitude modulator
Epsilon-near-zero (ENZ) metasurface
Indium tin oxide (ITO)
Plasmonic metasurface
Gap plasmon resonance
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