For many imaging applications installed on moving platforms, especially for smaller platforms without the advantage of large inertial mass, jitter is one the primary drivers in modulation transfer function (MTF) degradation. The use of an inertial measurement unit (IMU) to detect motion for non-blind deconvolution of imagery is not a new concept. However, most systems are focused on still photographs for small optical systems, such as cell phones, and are not focused on real-time implementation for full motion video (FMV) with dynamic systems that have multiple moving parts. Further, no existing system utilizes IMU information to intelligently decide when a camera system should integrate during the typical 33 ms framerate. Having control over when to integrate and for how long allows for greater signal-to-noise ratios (SNRs) at smaller jitters by selecting times when jitter is minimized based on the LOS motion. This work presents the framework of a jitter mitigation approach that both optimally decides on the integration window and implements non-blind deconvolution to produce a system that provides enhanced image resolution under a variety of conditions
Compact computational structure-function relations are needed to examine energy transfer between confined fields and carrier dynamics at heterostructure interfaces. This work used discrete dipole approximations to analyze quasiparticle excitation and dephasing at interfaces between metals and van der Waals materials. Simulations were compared with scanning transmission electron microscopy (STEM) for energy electron loss spectroscopy (EELS) at sub-nanometer resolution and femtosecond timescale. Artifacts like direct electron-hole pair generation were avoided. Comparing simulation with experiment distinguished quasiparticle energy transfer to hot carriers at the interface, and supported development of structure-function relations between interface morphology and emergent discrete and hybrid modes.
Compact structure-function simulations are needed to examine interactions between confined fields and carriers at interfaces of two-dimensional materials and metal contacts. This work used electron-source discrete dipole simulations of fields confined at metals interfaced with van der Waals materials to compare with measures using scanning transmission electron microscopy (STEM) for energy electron loss spectroscopy (EELS). Bright, dark, and hybrid modes at the interface were mapped at sub-nanometer resolution at resonant energies. Comparing simulation and measurement provided direct, femtosecond measures of confined field dephasing into carriers on topologically insulated surfaces for the first time.
Distinguishing contributions of physical and optical characteristics, and their interactions, to complicated features observed in spectra of nanocomposite plasmonic systems slows their implementation in optoelectronics. Use of vacuum, effective medium, or analytic approximations to compute such contributions are insufficient outside the visible spectrum (e.g., in energy harvesting) or for interfaces with complex dielectrics (e.g., semiconductors). This work synthesized discrete dipole computation of local physical/optical interaction with coupled dipole approximation of far-field Fano coupling to precisely distinguish effects of locally discontinuous dielectric environment and structural inhomogeneity on complicated spectra from a square lattice of gold nanospheres supported by complex dielectric substrates. Experimental spectra decomposition of resonant energies/bandwidths elucidated indium tin oxide affected surfaced plasmon resonance while silica affected diffractive coupled resonance features. Energy transport during plasmon decay was examined for each substrate under a variety of physical support configurations with the gold nanospheres. The compact, multi-scale approach can be adapted to arbitrary nanoantenna shapes (e.g., nanorings) interacting with various dielectrics (e.g., dichalcogenides). It offers >104-fold reduction in computation time over existing descriptions to accelerate the design and implementation of functional plasmonic systems.
Concentrating optics enable solar thermal energy to be harvested at high temperature (<100oC). As the temperature of the
receiver increases, radiative losses can become dominant. In many concentrating systems, the receiver is coated with a
selectively absorbing surface (TiNOx, Black Chrome, etc.) to obtain higher efficiency. Commercial absorber coatings are
well-developed to be highly absorbing for short (solar) wavelengths, but highly reflective at long (thermal emission)
wavelengths. If a solar system requires an analogous transparent, non-absorbing optic – i.e. a cover material which is
highly transparent at short wavelengths, but highly reflective at long wavelengths – the technology is simply not
available.
Low-e glass technology represents a commercially viable option for this sector, but it has only been optimized for visible
light transmission. Optically thin metal hole-arrays are another feasible solution, but are often difficult to fabricate. This
study investigates combinations of thin film coatings of transparent conductive oxides and nanoparticles as a potential
low cost solution for selective solar covers. This paper experimentally compares readily available materials deposited on
various substrates and ranks them via an ‘efficiency factor for selectivity’, which represents the efficiency of radiative
exchange in a solar collector. Out of the materials studied, indium tin oxide and thin films of ZnS-Ag-ZnS represent the
most feasible solutions for concentrated solar systems. Overall, this study provides an engineering design approach and
guide for creating scalable, selective, transparent optics which could potentially be imbedded within conventional low-e
glass production techniques.
A nanoparticle fluid filter used with concentrating hybrid solar/thermal collector design is presented. Nanoparticle fluid filters could be situated on any given concentrating system with appropriate customized engineering. This work shows the design in the context of a trough concentration system. Geometric design and physical placement in the optical path was modeled using SolTrace. It was found that a design can be made that blocks 0% of the traced rays. The nanoparticle fluid filter is tunable for different concentrating systems using various PV cells or operating at varying temperatures.
A spectral fluid filter for potential use in hybrid photovoltaic/thermal concentrating solar collectors has been developed, targeting maximum absorption above and transmission below a desired wavelength. In this application, the temperature-dependent bandgap of the potential solar cell is used in the optimization of the filter. Dispersing a mix of colloidal nanoparticles in a heat transfer fluid is shown to absorb 86% of sub-bandgap insolation while absorbing only 18% above bandgap insolation. Transmission above bandgap light would be directly absorbed into the photovoltaic (PV) cell while absorbed photons transfer energy directly into the heat transfer fluid ultimately reducing the number of heat transfer steps. Placement of a filter in front of the PV cell is shown to decrease losses by converting an additional 2% of the total solar energy into thermal energy since it allows recollection of light reflected off the receiver.
We propose a design for a concentrating PV/T collector utilizing plasmonic nanoparticles directly suspended in the working fluid to spectrally filter the incoming solar flux. This liquid filter serves two purposes: the direct capture of thermal energy as well as filtering off of key portions of the spectrum before transmission to the PV cell. Our device builds upon the current Cogenra T14 system with a two-pass architecture: the first pass on the back side of the PV cell pre-heating the fluid from any thermalization losses, and the second pass in front of the PV cell to achieve the spectral filtering. Here we present details on the selection of plasmonic nanoparticles for a given cell bandgap as well as the impact to the overall system pumping power and cost.
Rapid modeling of far-field Fano resonance supported by lattices of complex nanostructures is possible with the coupled
dipole approximation (CDA) using point, dipole polarizability extrapolated from a higher order discrete dipole
approximation (DDA). Fano resonance in nanostructured metamaterials has been evaluated with CDA for spheroids, for
which an analytical form of particle polarizability exists. For complex structures with non-analytic polarizability, such as
rings, higher order electrodynamic solutions must be employed at the cost of computation time. Point polarizability is
determined from the DDA by summing individual polarizable volume elements from the modeled structure. Extraction
of single nanoring polarizability from DDA permitted CDA analysis of nanoring lattices with a 40,000-fold reduction in
computational time over 1000 wavelengths. Maxima and minima of predicted Fano resonance energies were within 1%
of full volume elements using the DDA. This modeling technique is amenable to other complex nanostructures which
exhibit primarily dipolar and/or quadrupolar resonance behavior. Rapid analysis of coupling between plasmons and
photon diffraction modes in lattices of nanostructures supports design of plasmonic enhancements in sustainable energy
and biomedical devices.
Opto-electronic coupling of plasmonic nano-antennas in the near infrared water window in vitro and in vivo is of
growing interest for imaging contrast agents, spectroscopic labels and rulers, biosensing, drug-delivery, and optoplasmonic
ablation. Metamaterials composed of nanoplasmonic meta-atoms offer improved figures of merit in many
applications across a broader spectral window. Discrete and coupled dipole approximations effectively describe
localized and coupled resonance modes in nanoplasmonic metamaterials. From numeric and experimental results have
emerged four design principles to guide fabrication and implementation of metamaterials in bio-related devices and
systems. Resonance intensity and sensitivity are enhanced by surface-to-mass of meta-atoms and lattice constant. Fano
resonant coupling is dependent on meta-atom polarizability and lattice geometry. Internal reflection in plasmonic metaatom-
containing polymer films enhances dissipation rate. Dimensions of self-assembled meta-atoms depend on
balancing electrochemical and surface forces. Examples of these principles from our lab compare computation with
images and spectra from ordered metal-ceramic and polymeric nanocomposite metamaterials for bio/opto theranostic
applications. These principles speed design and description of new architectures for nanoplasmonic metamaterials that
show promise for bioapplications.
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