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Abstract

Nanophotonic all-optical switching is anticipated to replace electronic processing in future optical fibre front-end systems—unlocking capabilities for all-optical terabit-per-second processing. This work introduces a new all-optical switch (AOS) as a fundamental element for such processing. The AOS applies a nanophotonic superlens, in the form of a dielectric microsphere, to form an intense nonevanescent subdiffractional focus called a photonic nanojet. The photonic nanojet materializes in a coating of semiconductor nanoparticles at the rear of the microsphere. The AOS is refined using Lorenz- Mie theory simulations and free-carrier dynamical modelling. Experiments with microspheres coated by Si, CdTe, InP, and CuO nanoparticles, having radii of 40, 30, 20, and 20 nm, reveal switching energies of 1 pJ, 500 fJ, 400 fJ, and 300 fJ, and switching times of 2 ps, 2.3 ps, 900 fs, and 350 fs, respectively. The realized AOS meets the ultimate goals of femtojoule switching energies and femtosecond switching times.