113 research outputs found
Analysis of optical near-field energy transfer by stochastic model unifying architectural dependencies
We theoretically and experimentally demonstrate energy transfer mediated by
optical near-field interactions in a multi-layer InAs quantum dot (QD)
structure composed of a single layer of larger dots and N layers of smaller
ones. We construct a stochastic model in which optical near-field interactions
that follow a Yukawa potential, QD size fluctuations, and temperature-dependent
energy level broadening are unified, enabling us to examine
device-architecture-dependent energy transfer efficiencies. The model results
are consistent with the experiments. This study provides an insight into
optical energy transfer involving inherent disorders in materials and paves the
way to systematic design principles of nanophotonic devices that will allow
optimized performance and the realization of designated functions
Brightening of excitons in carbon nanotubes on dimensionality modification
Despite the attractive one-dimensional characteristics of carbon nanotubes, their typically low luminescence quantum yield, restricted because of their one-dimensional nature, has limited the performance of nanotube-based light-emitting devices. Here, we report the striking brightening of excitons (bound electron–hole pairs) in carbon nanotubes through an artificial modification of their effective dimensionality from one dimension to zero dimensions. Exciton dynamics in carbon nanotubes with luminescent, local zero-dimension-like states generated by oxygen doping were studied as model systems. We found that the luminescence quantum yield of the excitons confined in the zero-dimension-like states can be more than at least one order larger (~18%) than that of the intrinsic one-dimensional excitons (typically ~1%), not only because of the reduced non-radiative decay pathways but also due to an enhanced radiative recombination probability beyond that of intrinsic one-dimensional excitons. Our findings are extendable to the realization of future nanoscale photonic devices including a near-infrared single-photon emitter operable at room temperature
Nano-artifact metrics based on random collapse of resist
Artifact metrics is an information security technology that uses the
intrinsic characteristics of a physical object for authentication and clone
resistance. Here, we demonstrate nano-artifact metrics based on silicon
nanostructures formed via an array of resist pillars that randomly collapse
when exposed to electron-beam lithography. The proposed technique uses
conventional and scalable lithography processes, and because of the random
collapse of resist, the resultant structure has extremely fine-scale morphology
with a minimum dimension below 10 nm, which is less than the resolution of
current lithography capabilities. By evaluating false match, false non-match
and clone-resistance rates, we clarify that the nanostructured patterns based
on resist collapse satisfy the requirements for high-performance security
applications
Decision making based on optical excitation transfer via near-field interactions between quantum dots
Optical near-field interactions between nanostructured matter, such as
quantum dots, result in unidirectional optical excitation transfer when energy
dissipation is induced. This results in versatile spatiotemporal dynamics of
the optical excitation, which can be controlled by engineering the dissipation
processes and exploited to realize intelligent capabilities such as solution
searching and decision making. Here we experimentally demonstrate the ability
to solve a decision making problem on the basis of optical excitation transfer
via near-field interactions by using colloidal quantum dots of different sizes,
formed on a geometry-controlled substrate. We characterize the energy transfer
behavior due to multiple control light patterns and experimentally demonstrate
the ability to solve the multi-armed bandit problem. Our work makes a decisive
step towards the practical design of nanophotonic systems capable of efficient
decision making, one of the most important intellectual attributes of the human
brain
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