All-Optical Modulation in Chains of Silicon Nanoantennas

Dielectric nanoantennas represent a new branch of nanophotonics that allows efficient control of light scattering at nanoscale. Coupled nanoantennas can guide light on a chip over large distances without radiation losses, enabling a new nanoantenna-based silicon photonics platform with enchanced functionalities for light-on-chip integration. Here, an all-optical on-chip modulator based on a one-dimensional chain of silicon nanoantennas is proposed and experimentally demonstrated in the 1.55 μm telecommunication wavelength range. A resonator, with a quality factor up to 10⁴, is designed on the basis of a chain of coupled silicon nanoantennas, each supporting the electric dipole Mie resonance. Wafer-level fabrication of the nanoantennas is realized using CMOS compatible photolithography. High-speed modulation of the cavity mode is experimentally demonstrated via optical injection of free electrons and holes using a pulsed laser. The modulator is shown to have a response time of 50 ps and modulation depth beyond 25 dB, with 10 dB switching power being as low as ∼50 fJ. Low power and high-speed switching of the proposed device combined with the large-scale fabrication capabilities pave the way to applications of this dielectric nanoantenna-based approach to industrial on-chip photonics.