In this work, we summarize recent findings on ultrafast nonlinear and strong-field phenomena in silicon-loaded nanoplasmonic waveguides. Coupling ultrafast λ= 1:55 μm pulses into such structures gives rise to both high- efficiency third harmonic generation (THG) and ponderomotive electron acceleration. We show THG efficiencies of 2.3 ×10 5 in waveguides with an ultracompact footprint of 0.43 μm<sup>-2</sup>, resulting in visible green light emission. Remarkably, broadband white light emission is observed as well. This phenomenon is found to originate from an electron avalanche induced by the ponderomotive acceleration of electrons generated via two photon absorption. Thus, this nanoplasmonic device presents a versatile platform for realizing ultrafast nonlinear phenomenon within all-optical circuitry.
An antenna geometry that represents the contour of a traditional bowtie antenna is proposed and investigated via finitedifference
time-domain simulations. A parameter space consisting of the antenna length and the contour thickness is
explored and design principles for this geometry are presented. It is demonstrated that a continuous red-shift of the
resonant wavelength relative to the resonant wavelength of a bowtie antenna is possible by decreasing the contour
thickness of the antenna. In the parameter space examined, it is found that the antenna footprint may be reduced by a
factor of 3.6 and the gap enhancement factor may be increased by 28%. A conceptual understanding of the antenna
behavior is built up by drawing a parallel between the plasmonic nanoshell and the nanoplasmonic contour bowtie
antenna. Three other variations of this geometry are investigated in order to gain a deeper understanding of the
Several silicon-based plasmonic waveguides are proposed for long propagation and ultrafast all-optical modulation
and switching applications. Above-bandgap femtosecond pump pulses are used to generate free carriers in ion-implanted
silicon, resulting in ultrafast nonlinear phase and amplitude modulation. It is demonstrated that by
carefully designing a 5-layer device from silver, ion-implanted silicon and air, it is possible to achieve long
propagation distances (~100μm), or switching times of 5ps and an on-off contrast of 35dB.
We explore THz optical activity of ensembles of dense randomly oriented metallic helices by studying their time-domain response to THz electromagnetic pulse excitation. The interaction of the electromagnetic wave with this artificial chiral material mimics that interaction with highly concentrated optically active liquids. By dynamically accessing the THz electric field transmitted through the helical chiral media, optical activity signatures are correlated with the arrival time and polarization state of the detected THz electric field radiation. Our experiment show two distinct phases for optical rotation: one which is associated with scattering and the other is associated with phase accumulation.