Abstract
The transient optical response of multiresonant all‐dielectric nanoantennas via a combination of broadband ultrafast reflectivity experiments and nonlinear optics nanoscale modeling is studied. Ultrafast all‐optical control of the reflectivity is demonstrated in variably sized nanoantennas over four distinct Mie resonances (including Fano‐like resonances), spanning a broad spectral range, from the red to the near‐infrared. A spatially inhomogeneous dynamical model, which accounts for diffusion of the photogenerated carriers inside the semiconductor, is introduced and exploited to isolate the physical phenomena leading to the overall transient response, namely, Drude plasma formation and Pauli blocking following band filling and thermo‐optical effect. The results pave the way to the development of multiwavelength all‐optically reconfigurable filters for next‐generation ultrafast add/drop multiplexing.
Highlights
The transient optical response of multiresonant all-dielectric nanoantennas via a over the scattered optical fields
The transient optical response of multiresonant all-dielectric nanoantennas following the excitation with intense ultrashort laser pulses has been reported
The simultaneous all-optical control over four distinct resonances of Al.18Ga.82As nanopillars is experimentally demonstrated via broadband pump-probe spectroscopy
Summary
Among the many different platforms reported to date for alldielectric nanoantennas, those based on GaAs are promising because of the direct bandgap of the material, enabling efficient excitation with visible light. Due to the Fano resonance, the amplitude of the dips in the total reflectivity spectrum is significantly higher than the height of the peaks of the isolated nanopillars, showing that this mechanism is beneficial for obtaining strong resonant features This is especially true for higher order resonances (II, III, IV in Figure 1c) that tend to exhibit a more pronounced subradiant behavior. The spectrum exhibits sharp asymmetric dips, superimposed to broader strong modulations which are roughly 200 nm wide
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