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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Structure-dependent localized surface plasmon resonance characteristics and surface enhanced Raman scattering performances of quasi-periodic nanoarrays: Measurements and analysis

A set of periodic and quasi-periodic Au nanoarrays with different morphologies have been fabricated by using electron beam lithography technique, and their optical properties have been examined experimentally and analyzed theoretically by scanning near-field optical microscope and finite element method, respectively. Results present that the localized surface plasmon resonance of the as-prepared Au nanoarrays exhibit the structure-depended characteristics. Comparing with the periodic nanoarrays, the quasi-periodic ones demonstrate stronger electric field enhancement, especially for Thue-Morse nanoarray. Meanwhile, the surface enhanced Raman scattering (SERS) spectra of 4-mercaptobenzoic acid molecular labeled nanoarrays show that the quasi-periodic nanoarrays exhibit distinct SERS enhancement, for example, a higher enhancement factor of ∼10{sup 7} is obtained for the Thue-Morse nanoarray consisted of square pillars of 100 nm size. Therefore, it is significant to optimally design and fabricate the chip-scale quasi-periodic nanoarrays with high localized electric field enhancement for SERS applications in biosensing field.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Circular polarization analyzer with polarization tunable focusing of surface plasmon polaritons

A practical circular polarization analyzer (CPA) that can selectively focus surface plasmon polaritons (SPPs) at two separate locations, according to the helicity of the circularly polarized light, is designed and experimentally verified in the terahertz frequency range. The CPA consists of fishbone-slit units and is designed using the simulated annealing algorithm. By differentially detecting the intensities of the two SPPs focuses, the helicity of the incident circularly polarized light can be obtained and the CPA is less vulnerable to the noise of incident light. The proposed device may also have wide potential applications in chiral SPPs photonics and the analysis of chiral molecules in biology.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Plasmon-mediated circularly polarized luminescence of GaAs in a scanning tunneling microscope

The electroluminescence from p-type GaAs(110) in a scanning tunneling microscope has been investigated at 6 K. Unexpectedly, high degrees of circular polarization have often been observed with ferromagnetic Ni tips and also with paramagnetic W and Ag tips. The data are interpreted in terms of two distinct excitation mechanisms. Electron injection generates intense luminescence with low polarization. Plasmon-mediated generation of electron-hole pairs leads to less intense emission, which, however, is highly polarized for many tips.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Indium tin oxide refractometer in the visible and near infrared via lossy mode and surface plasmon resonances with Kretschmann configuration

An indium tin oxide (ITO) refractometer based on the generation of lossy mode resonances (LMRs) and surface plasmon resonances (SPRs) is presented. Both LMRs and SPRs are excited, in a single setup, under grazing angle incidence with Kretschmann configuration in an ITO thin-film deposited on a glass slide. The sensing capabilities of the device are demonstrated using several solutions of glycerin and water with refractive indices ranging from 1.33 to 1.47. LMRs are excited in the visible range, from 617 nm to 682 nm under TE polarization and from 533 nm to 637 nm under TM polarization, with a maximum sensitivity of 700 nm/RIU and 1200 nm/RIU, respectively. For the SPRs, a sensing range between 1375 nm and 2494 nm with a maximum sensitivity of 8300 nm/RIU is measured under TM polarization. Experimental results are supported with numerical simulations based on a modification of the plane-wave method for a one-dimensional multilayer waveguide.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Design of a hybrid silicon-plasmonic co-propagating coupler operating close to coherent perfect absorption

By hybrid integration of plasmonic and dielectric waveguide concepts, it is shown that nearly perfect coherent absorption can be achieved in a co-propagating coupler geometry. First, the operating principle of the proposed device is detailed in the context of a more general 2 × 2 lossy coupler formalism. Then, it is shown how to tune the device in a wide region of possible working points, its broadband operation, and the tolerance to fabrication uncertainties. Finally, a complete picture of the electromagnetic modes inside the hybrid structure is analyzed, shining light onto the potentials which the proposed device holds in view of classical and quantum signal processing, nonlinear optics, polarization control, and sensing.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Graphene based plasmonic terahertz amplitude modulator operating above 100 MHz

The terahertz (THz) region of the electromagnetic spectrum holds great potential in many fields of study, from spectroscopy to biomedical imaging, remote gas sensing, and high speed communication. To fully exploit this potential, fast optoelectronic devices such as amplitude and phase modulators must be developed. In this work, we present a room temperature external THz amplitude modulator based on plasmonic bow-tie antenna arrays with graphene. By applying a modulating bias to a back gate electrode, the conductivity of graphene is changed, which modifies the reflection characteristics of the incoming THz radiation. The broadband response of the device was characterized by using THz time-domain spectroscopy, and the modulation characteristics such as the modulation depth and cut-off frequency were investigated with a 2.0 THz single frequency emission quantum cascade laser. An optical modulation cut-off frequency of 105 ± 15 MHz is reported. The results agree well with a lumped element circuit model developed to describe the device.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Transfer of energy between a pair of molecules near a plasmonic core-shell nanoparticle: Tunability and sensing

Our model is applied to the calculation of interaction energy between a pair of dipolar molecules (point dipoles) in the vicinity of a nanoshell monomer with core-shell structure, based on the dipole quasi-electrostatic theory of classical electrodynamics and using the Drude and Maxwell-Garnett model. In other words, this work discusses the intermolecular energy transfer from a donor molecule to an acceptor molecule near a spherical nanoparticle that is important for practical applications like sensing. It is shown that the proximity of plasmonic nanoparticles can have a strong effect on the energy transfer between molecules. In addition to the influence of the size, composition, embedding medium, and the filling fraction of doped particles on the interaction energy, the contribution of the dipolar, quadrupolar, octupolar, hexadecapolar, triakontadipolar, and higher order multipole interactions is presented and analyzed. Briefly, we will show that it is possible to achieve enhanced energy transfer by manipulation of different parameters as mentioned above.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Plasmonic engineering of metal-oxide nanowire heterojunctions in integrated nanowire rectification units

We show that irradiation with femtosecond laser pulses can produce robust nanowire heterojunctions in coupled non-wetting metal-oxide Ag-TiO{sub 2} structures. Simulations indicate that joining arises from the effect of strong plasmonic localization in the region of the junction. Strong electric field effects occur in both Ag and TiO{sub 2} resulting in the modification of both surfaces and an increase in wettability of TiO{sub 2}, facilitating the interconnection of Ag and TiO{sub 2} nanowires. Irradiation leads to the creation of a thin layer of highly defected TiO{sub 2} in the contact region between the Ag and TiO{sub 2} nanowires. The presence of this layer allows the formation of a heterojunction and offers the possibility of engineering the electronic characteristics of interfacial structures. Rectifying junctions with single and bipolar properties have been generated in Ag-TiO{sub 2} nanowire circuits incorporating asymmetrical and symmetrical interfacial structures, respectively. This fabrication technique should be applicable for the interconnection of other heterogeneous metal-oxide nanowire components and demonstrates that femtosecond laser irradiation enables interfacial engineering for electronic applications of integrated nanowire structures.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Two-plasmon decay instability in inhomogeneous plasmas at oblique laser incidence

The two-plasmon decay (TPD) and stimulated Raman scattering (SRS) instabilities have been studied in the region near the quarter-critical density in the plasmas of the laser-driven inertial confinement fusion for a wide range of laser angles of incidence. The theoretical analysis of the TPD for oblique laser incidence has been carried out. The theoretical growth rates and thresholds have been compared with the results of the fluid-type simulations, and a good agreement has been found. Here, in the modeling including both TPD and SRS, the spectra of the growing perturbations have multiple peaks, and the maximum growth may be influenced by the interplay between TPD and SRS.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

10 nm gap bowtie plasmonic apertures fabricated by modified lift-off process

Bowtie plasmonic apertures, with gap sizes down to 11 nm and silver film thickness of up to 150 nm (aspect ratio ∼14:1), were fabricated on a silicon nitride membrane. Transmission spectra feature the aperture resonances ranging from 470 to 687 nm, with quality factors around 10. The mode area of the smallest gap aperture is estimated to be as small as 0.002 (λ/n)2 using numerical modeling. Importantly, our fabrication technique, based on an e-beam lithography and a lift-off process, is scalable which allows fabrication of many devices in parallel over a relatively large area. We believe that the devices demonstrated in this work will find application in studying and engineering light-matter interactions.

Huang, I-Chun↗
DOE OSTI2017

Simulations and measurements of hot-electron generation driven by the multibeam two-plasmon-decay instability

We report that multiple-beam experiments relevant to direct-drive inertial confinement fusion show the importance of nonlinear saturation mechanisms in the common-wave two-plasmon-decay (TPD) instability. Planar target experiments on the OMEGA laser used hard-x-ray measurements to study the influence of the linear common-wave growth rate on TPD driven hot-electron production in two drive beam configurations and over a range of overlapped laser intensities from 3.6 to 15.2 x 10 14 W/cm 2 . The beam configuration with the larger linear common-wave growth rate had a lower intensity threshold for the onset of hot-electron production, but the linear growth rate did not have a significant impact on hot-electron production at high intensities. The experiments were modeled in 3-D using a hybrid code (LPSE) that combines a wave solver with a particle tracker to self-consistently calculate the electron velocity distribution and evolve electron Landau damping. Finally, good quantitative agreement was obtained between the simulated and measured hotel-electron distributions using a novel technique to account for macroscopic spatial and temporal variations that are present in the experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Modeling optical coupling of plasmons and inhomogeneously broadened emitters

Optically coupling quantum emitters to nanoparticles provides the foundation for many plasmonic applications. Including quantum mechanical effects within the calculations can be crucial for designing new devices, but classical approximations are sometimes sufficient. Comprehending how the classical and quantum mechanical descriptions of quantum emitters alter their calculated optical response will lead to a better understanding of how to design devices. In this work, we describe how the semiclassical Maxwell-Liouville method can be used to calculate the optical response from inhomogeneously broadened states. After describing the Maxwell-Liouville algorithm, we use the method to study the photon echoes from quantum dots and compare the results against analytical models. We then modify the quantum dot’s state distribution to match a PbS 850 nm quantum dot’s absorption spectra to see how the complete quasi-band structure affects their coupling to gold nanoislands. Finally, we compare the results with previously published work to demonstrate where the complete quantum dot description is necessary.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Plasmonic absorption-induced haze suppression in random scattering media

Light propagation in random scattering media is a common phenomenon in many scientific and engineering fields. Because of light-matter interaction, part of the light transmitted through a random scattering medium is diffuse and causes haze. Previous approaches to manipulate haze in random media mainly focused on regulating scattering and paid little attention to absorption. In this work, we present a comprehensive analysis of absorption-scattering coupling as well as its impact on haze in random media. We introduce the haze-absorption sensitivity (HAS) spectrum, an intrinsic property of a scattering medium that quantifies the potential of absorption-induced haze suppression. We also investigate the effect of scatterer geometry and concentration on the HAS spectrum. To experimentally demonstrate the effect of absorption in random media, we utilized the plasmonic absorption of silver and gold nanoparticles to reduce haze in a silica nanoparticle aqueous solution as the scattering medium. We showed that 15% (absolute) of haze suppression is possible by carefully choosing the optimal absorber. The experimental results closely matched the theoretical predictions. This work provides new understandings of absorption and scattering coupling in random media. The fundamental mechanisms elucidated in this work can offer new pathways for regulating haze in a variety of random scattering media.

Zhao, Lin (ORCID:000000028865859X)↗
DOE OSTI2020

Impact of spatiotemporal smoothing on the two-plasmon–decay instability

Higher levels of hot electrons from the two-plasmon–decay instability are observed when smoothing by spectral dispersion (SSD) is turned off in directly driven inertial confinement fusion experiments at the Omega Laser Facility. This finding is explained using a hot-spot model based on speckle statistics and simulation results from the laser–plasma simulation environment. The model accurately reproduces the relative increase in hot-electron activity at two different drive intensities, although it slightly overestimates the absolute number of hot electrons in all cases. Extrapolating from the current ≈ 360-GHz system while adhering to the logic of the hot-spot model suggests that larger SSD bandwidth should significantly mitigate hot-electron generation, and legacy 1-THz OMEGA experiments appear to support this conclusion. These results demonstrate that it is essential to account for laser speckles and spatiotemporal smoothing to obtain quantitative agreement with experiments. A compilation of hot-electron data from the past two decades reveals several other important points: (1) many prior experiments are more easily understood using recent results from multibeam absolute instability theory; and (2) experiments with ignition-scale conditions produce less hot electrons compared to OMEGA spherical experiments for a given vacuum overlapped intensity, which is a promising result for validating performance predictions based on hydrodynamic scaling relations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Mitigation of hot-electron preheat from the two-plasmon-decay instability using silicon-doped plastic shells in direct-drive implosions on OMEGA

Hot electrons generated by the two-plasmon-decay (TPD) instability in laser-direct-drive implosions preheat the fuel and degrade performance. The mitigation of preheat using silicon-doped ablators (i.e., preheat is reduced by a factor of 1.40 ± 0.04) while decreasing the ratio of the laser spot diameter to the target diameter (⁠R b /R t⁠ ) to mitigate cross-beam energy transfer has been demonstrated on the OMEGA laser for quarter-critical laser intensities of 4.1 x 10 14 W/cm 2 ⁠, equivalent to an incident laser intensity of 8.3 x 10 14 W/cm 2 ⁠. The silicon dopant increases the electron temperature of the ablation plasma, which raises the intensity threshold for the onset of the TPD instability. These results show that implosion designs utilizing higher drive intensities can be used to achieve higher shell velocities, which are currently inaccessible with plastic ablators due to excessive preheat.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Correlating hot-electron preheat from the two-plasmon decay instability to $ρR$ degradation for direct-drive implosions on OMEGA

Focused experiments were performed with the goal of isolating the impact of hot-electron preheat on compression in deuterium–tritium (DT) layered, direct-drive implosions on OMEGA. Preheat from the hot-electrons generated by two-plasmon–decay (TPD) activity was varied through the incident laser intensity, with the total preheat energy deposited into unablated DT fuel being inferred using hard x-ray measurements. Results show a clear correlation between the inferred preheat levels and $ρR$ degradation that is consistent with a derived, 1D preheat model. A fit to the results also provides an estimated range of $ρR$ degradation from non-preheat sources for the adiabat ≈5 implosions used in this study. A follow-up study using targets containing Si-doped (5.5%) CH ablators (CHSi) demonstrated results consistent with mid-Z dopants mitigating TPD activity by showing these targets had almost no $ρR$ degradation as the laser intensity was increased up to levels previously considered damaging.

Doping↗
DOE OSTI2017

Single plasmonic split hole resonator nanostructure as an efficient nanoscale light source

We report a brief review of the results of experimental studies on the nonlinear optical interaction of laser radiation with a hybrid plasmonic nanostructure, i.e. a split hole resonator (SHR). We demonstrate second- and third-harmonic generation and mixed-frequency generation from a single SHR nanostructure. The practical application potential of an SHR nanostructure as a nanoprobe for measuring the femtosecond laser pulse duration and designing an all-optical nanodisplay is shown. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Symmetric nanostructuring and plasmonic excitation of gold nanostructures by femtosecond Laguerre – Gaussian laser beams

Femtosecond low-energy Laguerre – Gaussian pulses of tightly focused visible laser radiation were employed for single-pulse ablative nanostructuring of a 50-nm thick gold film. Similar pulses of lower energy were employed for the efficient plasmonic photoluminescence excitation of a rhodamine 6G dye monolayer in the fabricated nanostructures. The consistency between the shape and polarisation symmetries of the low-energy laser beam, on the one hand, and the gold nanostructures produced by the same beam at a high radiation energy, on the other hand, opens the way to consistent nanostructuring and surface-enhanced analytical spectroscopy with the use of nanostructures. (interaction of laser radiation with matter)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗