Ultrafast Hot-Electron Driven Plasmonic Modulation in Noble-Metal Nanoantenna High-Speed Optoelectronics

Ultrafast plasmonic modulators are becoming essential for next-generation optoelectronic systems, yet their speed is fundamentally limited by conventional semiconductor carrier dynamics. To address this bottle-neck, this study investigates hot-electron–driven plasmonic modulation in engineered noble-metal nanoantenna arrays, leveraging the sub-picosecond thermalization dynamics of non-equilibrium electrons to achieve femtosecond optical switching. The methodology integrates nanoscale fabrication of gold and silver dipole nanoantenna, resonant optical excitation, and time-resolved pump–probe spectroscopy, supported by a Multiphysics simulation framework combining the two-temperature model, plasmonic field enhancement, and electron–phonon coupling. Experimental results reveal a modulation speed below 200 fs with a modulation depth of 15–18%, accompanied by a rapid spectral shift in localized surface plasmon resonances, confirming the strong contribution of hot-electron–induced refractive index variation. The analysis further shows that enhanced confinement and asymmetric antenna geometry significantly increase hot-carrier density and improve switching performance without inducing thermal degradation. These insights demonstrate that hot-electron dynamics offer a viable pathway for scalable, ultrafast plasmonic modulators, enabling compact, broadband, and CMOS-compatible designs suitable for high-speed photonic interconnects, terahertz links, and on-chip optical switching.