Mode-locked laser diode with an ultrafast integrated uni-traveling carrier saturable absorber

Integration of photonic nanojets and semiconductor nanoparticles for enhanced all-optical switching

All-optical switching is the foundation of emerging all-optical (terabit-per-second) networks and processors. All-optical switching has attracted considerable attention, but it must ultimately support operation with femtojoule switching energies and femtosecond switching times to be effective. Here we introduce an all-optical switch architecture in the form of a dielectric sphere that focuses a high-intensity photonic nanojet into a peripheral coating of semiconductor nanoparticles. Milli-scale spheres coated with Si and SiC nanoparticles yield switching energies of 200 and 100 fJ with switching times of 10 ps and 350 fs, respectively. Micro-scale spheres coated with Si and SiC nanoparticles yield switching energies of 1 pJ and 20 fJ with switching times of 2 ps and 270 fs, respectively. We show that femtojoule switching energies are enabled by localized photoinjection from the photonic nanojets and that femtosecond switching times are enabled by localized recombination within the semiconductor nanoparticles.

The terabit-per-second rates of optical fibres exceed the capability of electronics, but all-optical switches are needed to alleviate the bottleneck in these networks. Here, Born et al. describe such a switch using dielectric spheres, yielding femtojoule switching energy and femtosecond switching times.