Ultrafast All-Optical Switching in III-V Semiconductor Resonant Nanostructures

All-dielectric high-index resonant nanostructures offer plentiful opportunities for tailoring characteristics of scattered radiation. In fact, the low level of ohmic losses at optical frequencies and the presence of pronounced magneto-dipolar modes in scattering spectra of dielectric nanoresonators pave the way to numerous scattering effects that could be employed for many practical applications [1]. To further advance the performance of dielectric nanophotonic devices, it is crucial to make them reconfigurable, i.e. to provide a method to manipulate optical properties of the material that they are made of. The electron-hole injection, carried out by optical means, is a promising solution for this task (Fig. 1A). Direct-gap semiconductors are perfectly suitable for that purpose, because this class of materials retains advantages typical for dielectrics and, at the same time, is defined by smaller bandgap widths, compared to dielectrics. The latter feature significantly decreases a value of the pumping pulse fluence that is required to noticeably change the optical response of a resonant nanostructure. Indeed, it was numerically shown that the change of the trajectory of the probing pulse constituted 20° for an asymmetric dimer comprised of two silicon (Si) spheres of different radii for the energy fluence of the pumping pulse Φ si = 1.6 mJ cm−2 [2]. On the other hand, there is an experimental study of all-optical switching in gallium arsenide (GaAs) metasurface that indicated the change of its reflection coefficient ΔR = 0.35 for the fluence Φ GaAs = 0.31 mJ cm−2 [3].