Engineering Localized Surface Plasmon Interactions in Gold by Silicon Nanowire for Enhanced Heating and Photocatalysis.

The field of plasmonics has attracted considerable attention in recent years because of potential applications in various fields such as nanophotonics, photovoltaics, energy conversion, catalysis, and therapeutics. It is becoming increasing clear that intrinsic high losses associated with plasmons can be utilized to create new device concepts to harvest the generated heat. It is therefore important to design cavities, which can harvest optical excitations efficiently to generate heat.

Tailoring the Spectroscopic Properties of Semiconductor Nanowires via Surface-Plasmon-Based Optical Engineering.

Semiconductor nanowires, due to their unique electronic, optical, and chemical properties, are firmly placed at the forefront of nanotechnology research. The rich physics of semiconductor nanowire optics arises due to the enhanced light-matter interactions at the nanoscale and coupling of optical modes to electronic resonances. Furthermore, confinement of light can be taken to new extremes via coupling to the surface plasmon modes of metal nanostructures integrated with nanowires, leading to interesting physical phenomena.

Enhanced second-harmonic generation from metal-integrated semiconductor nanowires via highly confined whispering gallery modes.

Coherent and tunable nanoscale light sources utilizing optical nonlinearities are required for applications ranging from imaging and bio-sensing to on-chip all-optical signal processing. However, owing to their small sizes, the efficiency of nanostructures even with high nonlinear coefficients is poor, therefore requiring very high excitation energies. Although surface-plasmon resonances of metal nanostructures can enhance surface nonlinear processes such as second-harmonic generation, they still suffer from low conversion efficiencies owing to their intrinsically low nonlinear coefficients.

Studies of hot photoluminescence in plasmonically coupled silicon via variable energy excitation and temperature-dependent spectroscopy.

By integrating silicon nanowires (∼150 nm diameter, 20 μm length) with an Ω-shaped plasmonic nanocavity, we are able to generate broadband visible luminescence, which is induced by high order hybrid nanocavity-surface plasmon modes. The nature of this super bandgap emission is explored via photoluminescence spectroscopy studies performed with variable laser excitation energies (1.959 to 2.

Tailoring light-matter coupling in semiconductor and hybrid-plasmonic nanowires.

Understanding interactions between light and matter is central to many fields, providing invaluable insights into the nature of matter. In its own right, a greater understanding of light-matter coupling has allowed for the creation of tailored applications, resulting in a variety of devices such as lasers, switches, sensors, modulators, and detectors. Reduction of optical mode volume is crucial to enhancing light-matter coupling strength, and among solid-state systems, self-assembled semiconductor and hybrid-plasmonic nanowires are amenable to creation of highly-confined optical modes.

Silicon coupled with plasmon nanocavity generates bright visible hot-luminescence.

Due to limitations in device speed and performance of silicon-based electronics, silicon optoelectronics has been extensively studied to achieve ultrafast optical-data processing. However, the biggest challenge has been to develop an efficient silicon-based light source since indirect band-gap of silicon gives rise to extremely low emission efficiency. Although light emission in quantum-confined silicon at sub-10 nm lengthscales has been demonstrated, there are difficulties in integrating quantum structures with conventional electronics.

Tailoring hot-exciton emission and lifetimes in semiconducting nanowires via whispering-gallery nanocavity plasmons.

The manipulation of radiative properties of light emitters coupled with surface plasmons is important for engineering new nanoscale optoelectronic devices, including lasers, detectors and single photon emitters. However, so far the radiative rates of excited states in semiconductors and molecular systems have been enhanced only moderately, typically by a factor of 10-50, producing emission mostly from thermalized excitons. Here, we show the generation of dominant hot-exciton emission, that is, luminescence from non-thermalized excitons that are enhanced by the highly concentrated electromagnetic fields supported by the resonant whispering-gallery plasmonic nanocavities of CdS-SiO(2)-Ag core-shell nanowire devices.

Variable temperature spectroscopy of as-grown and passivated CdS nanowire optical waveguide cavities.

Semiconductor nanowire waveguide cavities hold promise for nanophotonic applications such as lasers, waveguides, switches, and sensors due to the tight optical confinement in these structures. However, to realize their full potential, high quality nanowires, whose emission at low temperatures is dominated by free exciton emission, need to be synthesized. In addition, a proper understanding of their complex optical properties, including light-matter coupling in these subwavelength structures, is required.