N. J. Phys. 14, 093005 (2012)

Optical nano-antennas allow the manipulation of optical fields at the subwavelength scale, providing control over the direction of emitted light that can be of benefit in many applications including sensing and solar cells. Now a theoretical study from Roman Noskov and colleagues from Russia and Australia has shed light on a hybrid metal–dielectric nano-antenna that allows for dynamic control over its scattering pattern. In particular, the radiation pattern can be reversed by varying the external field intensity, offering potential for ultrafast all-optical switching. The hybrid system consists of nanoparticles made of silver, chosen for its relatively low loss and high nonlinear susceptibility, and crystalline silicon, which is a high-permittivity dielectric. The intrinsic nonlinearities of the silver particles lead to different polarizabilities of the metal and dielectric nanoparticles. This in turn imparts a phase shift between the dipole moments of the nanoparticles, resulting in the ability to switch between the forward and backward directions of the radiation pattern. Numerical simulations by the researchers reveal that the system possesses a switching time of just 40 fs. Comparing this with present switching times, of a few picoseconds, this hybrid seems to be an ultrafast alternative.