Broadband electro-optic intensity modulators are essential to convert electrical signals to the optical domain. The growing interest in terahertz wireless applications demands modulators with frequency responses to the sub-terahertz range, high power handling, and very low nonlinear distortions, simultaneously. However, a modulator with all those characteristics has not been demonstrated to date. Here, we experimentally demonstrate that plasmonic modulators do not trade-off any performance parameter, featuring—at the same time—a short length of tens of micrometers, record-high flat frequency response beyond 500 GHz, high power handling, and high linearity, and we use them to create a sub-terahertz radio-over-fiber analog optical link. These devices have the potential to become a new tool in the general field of microwave photonics, making the sub-terahertz range accessible to, e.g., 5G wireless communications, antenna remoting, Internet of Things, sensing, and more.

Ultrafast plasmonic modulation: Plasmonics converts light into propagating electrical signals. This approach could allow us to shrink optical components to the nanometer scale, far below the hundreds of wavelengths typically set by conventional optics. Ayataet al.fabricated a plasmonic modulator from a single layer of gold using a substrate-independent process. They created a device with a footprint less than the cross-sectional area of a human hair and with modulation rates exceeding 100 GHz, which could provide a flexible platform for future ultrafast plasmonic technology.Science, this issue p.630

Electro-optic modulators are essential for sensing, metrology and telecommunications. Most target fiber applications. Instead, metasurface-based architectures that modulate free-space light at gigahertz (GHz) speeds can boost flat optics technology by microwave electronics for active optics, diffractive computing or optoelectronic control. Current realizations are bulky or have low modulation efficiencies. Here, we demonstrate a hybrid silicon-organic metasurface platform that leverages Mie resonances for efficient electro-optic modulation at GHz speeds. We exploit quasi bound states in the continuum (BIC) that provide narrow linewidth (Q = 550 at $${\lambda }_{{{{{{{{\rm{res}}}}}}}}}=1594$$λ res = 1594 nm), light confinement to the non-linear material, tunability by design and voltage and GHz-speed electrodes. Key to the achieved modulation of $$\frac{{{\Delta }}T}{{T}_{\max }}=67 \%$$Δ T T max = 67 % are molecules with r₃₃ = 100 pm/V and optical field optimization for low-loss. We demonstrate DC tuning of the resonant frequency of quasi-BIC by $${{\Delta }}{\lambda }_{{{{{{{{\rm{res}}}}}}}}}=$$Δ λ res = 11 nm, surpassing its linewidth, and modulation up to 5 GHz (f_EO,−3dB = 3 GHz). Guided mode resonances tune by $${{\Delta }}{\lambda }_{{{{{{{{\rm{res}}}}}}}}}=$$Δ λ res = 20 nm. Our hybrid platform may incorporate free-space nanostructures of any geometry or material, by application of the active layer post-fabrication.