8 research outputs found
Studies of hot photoluminescence in plasmonically-coupled silicon via variable energy excitation and temperature dependent spectroscopy
By coupling silicon nanowires (~150 nm diameter, 20 micron length) with an
{\Omega}-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 eV to 2.708 eV) and finite difference time domain simulations.
Furthermore, temperature-dependent photoluminescence spectroscopy shows that
the observed emission corresponds to radiative recombination of un-thermalized
(hot) carriers as opposed to a Resonant Raman process
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. Following development of unique spectroscopic techniques designed for the nanowire morphology, carefully engineered semiconductor nanowire cavities have recently been tailored to enhance light-matter coupling strength in a manner previously seen in optical microcavities. Much smaller mode volumes in tailored hybrid-plasmonic nanowires have recently allowed for similar breakthroughs, resulting in sub-picosecond excited-state lifetimes and exceptionally high radiative rate enhancement. Here, we review literature on light-matter interactions in semiconductor and hybrid-plasmonic monolithic nanowire optical cavities to highlight recent progress made in tailoring light-matter coupling strengths. Beginning with a discussion of relevant concepts from optical physics, we will discuss how our knowledge of light-matter coupling has evolved with our ability to produce ever-shrinking optical mode volumes, shifting focus from bulk materials to optical microcavities, before moving on to recent results obtained from semiconducting nanowires.
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
2.708 eV) and finite difference time domain simulations. Furthermore,
temperature-dependent photoluminescence spectroscopy shows that the
observed emission corresponds to radiative recombination of unthermalized
(hot) carriers as opposed to a resonant Raman process
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.
We report a highly engineered nanowire cavity, which utilizes a high
dielectric silicon core with a thin plasmonic film (Au) to create
an effective metallic cavity to strongly confine light, which when
coupled with localized surface plasmons in the nanoparticles of the
thin metal film produces exceptionally high temperatures upon laser
irradiation. Raman spectroscopy of the silicon core enables precise
measurements of the cavity temperature, which can reach values as
high as 1000 K. The same Si–Au cavity with enhanced plasmonic
activity when coupled with TiO<sub>2</sub> nanorods increases the
hydrogen production rate by ∼40% compared to similar Au–TiO<sub>2</sub> system without Si core, in ethanol photoreforming reactions.
These highly engineered thermoplasmonic devices, which integrate three
different cavity concepts (high refractive index core, metallo-dielectric
cavity, and localized surface plasmons) along with the ease of fabrication
demonstrate a possible pathway for designing optimized plasmonic devices
with applications in energy conversion and catalysis
Silicon coupled with plasmon nanocavities 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(1–3). 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(4–7), there are difficulties in integrating quantum structures with conventional electronics(8,9). It is desirable to develop new concepts to obtain emission from silicon at lengthscales compatible with current electronic devices (20-100 nm), which therefore do not utilize quantum-confinement effects. Here, we demonstrate an entirely new method to achieve bright visible light emission in “bulk-sized” silicon coupled with plasmon nanocavities from non-thermalized carrier recombination. Highly enhanced emission quantum efficiency (>1%) in plasmonic silicon, along with its size compatibility with present silicon electronics, provides new avenues for developing monolithically integrated light-sources on conventional microchips