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arXiv · 2509.09173

Giant near-field nonlinear electrophotonic effects in an angstrom-scale plasmonic junction

Shota Takahashi·Atsunori Sakurai·Tatsuto Mochizuki·Toshiki Sugimoto
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Abstract

Plasmons facilitate a strong confinement and enhancement of near-field light, offering exciting opportunities to enhance nonlinear optical responses at the nanoscale. However, despite significant advancements, the electrically tunable range of the nonlinear optical responses at nanometer-scale plasmonic structures remains limited to a few percents per volt. Here, we transcend the limitation of the nanometer regime by expanding the concept of electrophotonics into angstrom-scale platform, enabling high-performance modulation of near-field nonlinear optical responses inaccessible in prior architectures. We demonstrate ~2000% enhancement in second-harmonic generation (SHG) within 1 V of voltage application by utilizing an angstrom-scale plasmonic gap between a metallic tip and a flat metal substrate in a scanning tunneling microscope. Extending this near-field SHG scheme to sum-frequency generation that is accompanied by large frequency upconversion, we also found that such giant electrical modulation of plasmon-enhanced nonlinear optical phenomena is effective over mid-infrared to visible broad wavelength range. Our results and concepts lay the foundation for developing near-field-based angstrom-scale nonlinear electrophotonics with significant modulation depth at low driving voltage.

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Shota Takahashi, Atsunori Sakurai, Tatsuto Mochizuki, Toshiki Sugimoto. 2025-09-11. Giant near-field nonlinear electrophotonic effects in an angstrom-scale plasmonic junction. https://doi.org/10.1038/s41467-026-68823-4

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