S. Sederberg

Sierpiński fractal plasmonic antenna: a fractal abstraction of the plasmonic bowtie antenna

A new class of bowtie antennas with Sierpiński fractal features is proposed for sensing molecular vibration modes in the near- to mid-infrared. These antennas offer a compact device footprint and an enhanced confinement factor compared to a bowtie antenna. Through extensive simulations, it is shown that these characteristics are related to the ability of this fractal geometry to become polarized. Simulation results demonstrate that these antennas may be tuned between 700 nm ≤ λ ≤ 3.4 µm and that electric field enhancement by 56 is possible at the center of the antenna gap.

Nanoscale plasmonic contour bowtie antenna operating in the mid-infrared.

A plasmonic antenna design is proposed and investigated numerically over a large parameter space. By considering the contour of a bowtie antenna and introducing an additional design parameter, the contour thickness, it is demonstrated that the resonant wavelength of the antenna may be tuned over a broad spectral range while maintaining a constant antenna footprint. These new antennas allow for a factor of 3.6 reduction in the antenna footprint and an increase in the gap enhancement by 28%.

Monolithic integration of plasmonic waveguides into a complimentary metal-oxide-semiconductor- and photonic-compatible platform

A silicon-based plasmonic waveguide was designed and fabricated for use at telecommunications wavelengths. This waveguide is interfaced to the silicon photonics platform by use of a tapered silicon-on-insulator waveguide. Simulations indicate that this scheme excites the transverse magnetic plasmonic mode and that the electric fields are confined to the silicon-gold interface. Transmitted power is measured for several device lengths and the propagation distance and coupling efficiency are found to be 2.00 μm and 38.0%, respectively. These results demonstrate the potential for integration between silicon photonics and silicon plasmonic devices and demonstrate the ability to incorporate silicon-based plasmonic devices into complimentary metal-oxide-semiconductor electronic and photonic circuitry.

Ultrafast all-optical switching in a silicon-based plasmonic nanoring resonator

A silicon-based plasmonic nanoring resonator is proposed for ultrafast, all-optical switching applications. Full-wave numerical simulations demonstrate that the photogeneration of free carriers enables ultrafast switching of the device by shifting the transmission minimum of the resonator with a switching time of 3 ps. The compact 1.00 μm² device footprint demonstrates the potential for high integration density plasmonic circuitry based on this device geometry.

Ultrafast all-optical modulation in silicon-based nanoplasmonic devices.

A five-layer silicon-based nanoplasmonic waveguiding structure is proposed for ultrafast all-optical modulation and switching applications. Ultrafast nonlinear phase and amplitude modulation is achieved via photo-generated free carrier dynamics in ion-implanted silicon using above-bandgap femtosecond pump pulses. Both an analytical model and rigorous numerical simulations of the structures have shown that a switching time of 5 ps and an on-off contrast of 35 dB can be achieved in these devices.

Optical activity in an artificial chiral media: a terahertz time-domain investigation of Karl F. Lindman’s 1920 pioneering experiment

Chiral media interact preferentially with either left- or right-circularly polarized electromagnetic waves, leading to effects including circular dichroism, optical rotation and circular preferential scattering. In this experiment, we revisit Lindmans famous 1920 experiment linking artificial chiral materials to optical activity and we record the first time-domain measurements of a single-cycle THz pulse transmitted through randomly oriented metallic helices. Time-resolved measurements of co- and cross-polarized components of the transmitted electric field allow the electric field trajectory to be reconstructed and time dynamics of the two circular components to be investigated. For the first time, we show that time dynamics reveal two distinct effects that are separated in time: local preferential circular scattering and collective coupling. These findings are important on furthering our understanding on the analogy between optical activity arising from light interaction with large chiral molecules and that from macroscopic artificial chiral media.

The influence of Hausdorff dimension on plasmonic antennas with Pascal’s triangle geometry

We introduce fractal geometry to the common bowtie antenna and investigate the influence of a key fractal parameter, Hausdorff dimension, on the broadband spectral response of the antenna. Length scaling trends are presented for antennas having various Hausdorff dimensions. We show that antennas with Pascal’s triangle geometry accommodate resonances that are red-shifted when compared to a standard bowtie antenna having the same size. Furthermore, increasing the Hausdorff dimension of the antenna blue shifts its resonance. By designing nanoplasmonic antennas with Pascal’s triangle geometry, the resonance conditions may be varied while the antenna dimensions are kept constant.

Integrated nanoplasmonic waveguides for magnetic, nonlinear, and strong-field devices

Abstract As modern complementary-metal-oxide-semiconductor (CMOS) circuitry rapidly approaches fundamental speed and bandwidth limitations, optical platforms have become promising candidates to circumvent these limits and facilitate massive increases in computational power. To compete with high density CMOS circuitry, optical technology within the plasmonic regime is desirable, because of the sub-diffraction limited confinement of electromagnetic energy, large optical bandwidth, and ultrafast processing capabilities. As such, nanoplasmonic waveguides act as nanoscale conduits for optical signals, thereby forming the backbone of such a platform. In recent years, significant research interest has developed to uncover the fundamental physics governing phenomena occurring within nanoplasmonic waveguides, and to implement unique optical devices. In doing so, a wide variety of material properties have been exploited. CMOS-compatible materials facilitate passive plasmonic routing devices for directing the confined radiation. Magnetic materials facilitate time-reversal symmetry breaking, aiding in the development of nonreciprocal isolators or modulators. Additionally, strong confinement and enhancement of electric fields within such waveguides require the use of materials with high nonlinear coefficients to achieve increased nonlinear optical phenomenon in a nanoscale footprint. Furthermore, this enhancement and confinement of the fields facilitate the study of strong-field effects within the solid-state environment of the waveguide. Here, we review current state-of-the-art physics and applications of nanoplasmonic waveguides pertaining to passive, magnetoplasmonic, nonlinear, and strong-field devices. Such components are essential elements in integrated optical circuitry, and each fulfill specific roles in truly developing a chip-scale plasmonic computing architecture.

Ultrafast nonlinear and strong-field phenomena in silicon-loaded nanoplasmonic waveguides

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-2, 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.

Strong-field phenomena in silicon nanoplasmonic waveguides

A current debate among the CMOS and electronic and electronic-photonic integrated circuit communities centers on the idea that nanoplasmonic components cannot replace conventional electronics or their optical counterparts without a means of making silicon (Si) technology amenable to strong nonlinear plasmonic interactions. For monolithic integration with CMOS, silicon photonic devices must be reduced to dimensions that are below the diffraction limit, especially with the current 14nm feature size of modern nanoelectronics. However, the optical diffraction limit imposes a bound on radiation intensity, which restricts the attainable field strength necessary to exploit nonlinear processes in silicon-based devices. Consequently, bridging both CMOS electronics and silicon photonic technologies requires a new approach, such as nonlinear silicon nanoplasmonics. Nanoplasmonics enables waveguiding devices to achieve compact nanoscale footprints with dimensions below the diffraction limit of light. This would allow for high integration densities and access to nonlinear processes such as two-photon absorption, free-carrier absorption, Raman amplification, the optical Kerr effect, and four-wave mixing through high optical mode confinement. For these reasons, nanoplasmonics is believed to have great potential for the next generation of silicon-based optical computing. Accessing a highly nonlinear field-matter regime entails the use of high-power laser sources. Recently, our attention has focused on high-field interactions in nanoscale systems without the need for such sources.1–5 In this respect, a strong-field nanoplasmonic phenomenon has emerged that brings extreme nonlinear light-matter interactions into the realm of nanoscale science. The development is revealing exciting new physics, in Figure 1. Scanning electron micrograph of the silicon (Si)-loaded gold (Au) nanoplasmonic waveguide. The structure is fabricated on a silicon-on-insulator wafer.