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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Analysis on vertical directional couplers with long range surface plasmons for multilayer optical routing

A structure featuring vertical directional coupling of long-range surface plasmon polaritons between strip waveguides at λ = 1.55 μm is investigated with the aim of producing efficient elements that enable optical multilayer routing for 3D photonics. We have introduced a practical computational method to calculate the interaction on the bent part. This method allows us both to assess the importance of the interaction in the bent part and to control it by a suitable choice of the fabrication parameters that helps also to restrain effects due to fabrication issues. The scheme adopted here allows to reduce the insertion losses compared with other planar and multilayer devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Time resolved detection of two-plasmon decay using three-halves harmonic emission on the National Ignition Facility

Supra-thermal (>100 keV) electrons generated by laser plasma interactions can be detrimental to the performance of ignition experiments conducted on the National Ignition Facility (NIF). On a NIF shot, the amount of electrons is estimated by measuring the hard X-rays passing through the hohlraum wall. The primary sources of hot electrons in a hohlraum are Stimulated Raman Scattering (SRS) and two plasmon decay (TPD). While SRS is well diagnosed on the NIF, there has been no diagnosis of TPD. Here we have designed and implemented a new diagnostic to characterize the time history of TPD on the NIF. The instrument provides a time resolved measurement of the 3/2 ω harmonic emission which is indicative of the presence of TPD. We describe the diagnostic setup, calibration, and the preliminary results obtained on NIF hohlraum experiments. Finally, we find evidence of a correlation between measured hard X-rays generated from the hot electron bremsstrahlung and the TPD emission.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Phonon-induced plasmon-exciton coupling changes probed via oscillation-associated spectra

Coherent vibrations detected in optical experiments can offer insights into material properties and electronic interactions, but also yield complex time-dependent optical signatures, especially in hybridized systems. In this work, we conform to techniques from studies on vibrational wave packets in molecules to analyze the optical signatures of coherent acoustic phonons in nanoparticles. This strategy enables us to better understand the implications of energetic changes induced by coherent phonons. Then, we apply this approach to systems that target coherent acoustic phonons as a route to modulate plasmon-exciton coupling and compare the results to theoretical calculations. Taken together, the described approach provides an intuitive, simple means of analyzing future systems and facilitates attempts to utilize, rather than simply observe, nanomaterial phonon modes.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Phase control of coherent acoustic phonons in gold bipyramids for optical memory and manipulating plasmon–exciton coupling

Recent efforts have targeted manipulation of nanomaterial vibrational modes in applications such as chemical/mass sensing, optical switching, and phonon-driven photochemistry. While impulsive photoexcitation can generate coherent phonons, multiple excitation pulses offer the prospect of control and manipulation of coherent phonon modes for functions of optical memory and logic. In this work, we use such an approach to inject an arbitrary coherent phonon phase into a colloidal ensemble of highly monodisperse gold bipyramids. We then demonstrate that this technique can be applied to a system that exhibits plasmon-exciton coupling to further manipulate the hybridization of the system. This ability to manipulate acoustic phonons and hybridization can enable optical logic applications of acoustic phonons in addition to optical memory.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Femtosecond photoemission electron microscopy of surface plasmon polariton beam steering via nanohole arrays

Directional control over surface plasmon polariton (SPP) waves is a prerequisite for the development of miniaturized optical circuitry. Here, the efficacy of single and dual component SPP steering elements is explored through photoemission electron microscopy. Our imaging scheme relies on two-color photoemission and counter-propagating SPP generation, which collectively allow SPPs to be visualized in real space. Wave-vector difference mixing between two-dimensional arrays of nanoholes and photon momenta enables SPP steering with directionality governed by the array lattice constant. The magnitude of grating momentum required to achieve counter-propagation guarantees efficient steering over the full range of the negative half-space. In our dual component configuration, separate SPP generation and Bragg diffraction based steering optics are employed. We find that array Bragg planes principally influence the SPP angles through the array band structure, which allows us to visualize both positive and negative refractory waves.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Excitation of a plasmon resonance in metal cylinders by an evanescent wave

The magnetic field distribution and electric-field amplification factor are found in the gap between periodically arranged parallel metal cylinders scattering an evanescent wave. Such a wave appears if an original plane wave is incident from the dielectric substrate onto the interface at an angle of total internal reflection. A substantial restructuring of the near-field distribution, which results from a small change in the angle of incidence, is revealed. Estimations of the angular dependence of the local field, explaining the shift and broadening of the plasmon resonance at a shorter wavelength, are presented. (nanostructures)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Efficiency of surface plasmon excitation at the photonic crystal – metal interface

We report the results of a theoretical investigation of light wave transformation in a one-dimensional photonic crystal. The scheme considered comprises an incident wave directed in parallel with layers of the photonic crystal under an assumption that the wave vector is far from a forbidden zone. Expressions for propagating and evanescent electromagnetic waves in a periodic medium of the photonic crystal are obtained. It is found that the transverse structure of the propagating wave comprises a strong constant component and a weak oscillating component with a period determined by that of the photonic crystal. On the contrary, the dependence of evanescent waves on transverse coordinates is presented by a strong oscillating component and a weak constant component. The process of transformation of propagating waves to evanescent waves at a crystal – metal interface is investigated. Parameters of the photonic crystal typical for synthetic opals are used in all numerical simulations. The theoretical approach elaborated yields in an explicit form the dependence of the amplitude of a generated surface wave on the period of the dielectric function modulation in the photonic crystal. The results obtained show that in the conditions close to plasmon resonance the amplitude of the surface wave may be on the order of or even exceed that of the initial incident wave. (light wave transformation)

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Light absorption and plasmon – exciton interaction in three-layer nanorods with a gold core and outer shell composed of molecular J- and H-aggregates of dyes

Optical properties of hybrid rod-like nanoparticles, consisting of a gold core, an intermediate passive organic layer (spacer) and outer layer of ordered molecular cyanine dye aggregates, are experimentally and theoretically investigated. It is shown that these dyes can form not only ordered J-aggregates but also H-aggregates (differing by the packing angle of dye molecules in an aggregate and having other spectral characteristics) in the outer shell of the hybrid nanostructure. Absorption spectra of synthesised three-layer nanorods are recorded, and their sizes are determined. The optical properties of the composite nanostructures under study are found to differ significantly, depending on the type of the molecular aggregate formed in the outer shell. The experimental data are quantitatively explained based on computer simulation using the finite-difference time-domain (FDTD) method, and characteristic features of the plasmon – exciton interaction in the systems under study are revealed. (nanophotonics)

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Third harmonic generation in the short-wavelength UV range by a single plasmonic nanostructure

The nonlinear optical interaction of laser radiation with nanostructures formed in gold and aluminium nanofilms has been experimentally studied. It is shown that, despite the high susceptibility χ{sub 3} of aluminium in comparison with gold, the third-harmonic generation efficiency at a wavelength of 260 nm is much higher for the nanostructures formed in a gold nanofilm because of the efficient excitation of a localised plasmon resonance at the fundamental frequency. (extreme laser radiation: physics and fundamental applications)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Reflection of terahertz monochromatic surface plasmon-polaritons by a plane mirror

Using a free electron laser developed in Novosibirsk, we have studied the reflection of monochromatic ( λ = 130 μm) surface plasmon-polaritons (SPPs) from a plane mirror attached to a waveguiding surface. It is found that 100 % SPP reflection occurs not only in the perpendicular position of the mirror relative to the surface, but also when the mirror is deflected from the normal by the angle α being smaller than the limiting angle α * proportional to the SPP wave vector. When the mirror is deflected by the angle greater than α *, SPPs on a perfectly smooth surface must transform into a bulk wave, while, in the experiment, the SPP reflection coefficient decreases gradually to zero with increasing α , which is a manifestation of dispersion of the wave vector of monochromatic SPPs, caused by their scattering on the inhomogeneities of a real surface. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Observation of surface plasmon resonance of gold nanoparticles in energy-related material: pentaerythritol tetranitrate

The surface plasmon resonance of gold nanoparticles in a polycrystalline energy-related material – pentaerythritol tetranitrate (PETN) – has been observed for the first time. The extinction spectra of this material are recorded, and its absorption characteristics are determined by the photoacoustic method using pulsed laser irradiation. Using the data obtained, it is concluded that gold nanoparticles are promising inclusions in explosive materials when designing an optical detonator. (paper)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Coherent emission from surface Josephson plasmons in striped cuprates

The interplay between charge order and superconductivity remains one of the central themes of research in quantum materials. In the case of cuprates, the coupling between striped charge fluctuations and local electromagnetic fields is especially important, as it affects transport properties, coherence, and dimensionality of superconducting correlations. Here, we study the emission of coherent terahertz radiation in single-layer cuprates of the La 2-x Ba x CuO 4 family, for which this effect is expected to be forbidden by symmetry. We find that emission vanishes for compounds in which the stripes are quasi-static but is activated when c-axis inversion symmetry is broken by incommensurate or fluctuating charge stripes, such as in La 1.905 Ba 0.095 CuO 4 and in La 1.845 Ba 0.155 CuO 4 . In this case, terahertz radiation is emitted by surface Josephson plasmons, which are generally dark modes, but couple to free space electromagnetic radiation because of the stripe modulation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Characterization of plasmonic hole arrays as transparent electrical contacts for organic photovoltaics using high-brightness Fourier transform methods

Here we present a methodology for probing light-matter interactions in prototype photovoltaic devices consisting of an organic semiconductor active layer with a semitransparent metal electrical contact exhibiting surface plasmon-based enhanced optical transmission. We achieve high-spectral irradiance in a spot size of less than 100 μm using a high-brightness laser-driven light source and appropriate coupling optics. Spatially resolved Fourier transform photocurrent spectroscopy in the visible and near-infrared spectral regions allows us to measure external quantum efficiency with high sensitivity in small-area devices (<1 mm 2 ). Lastly, this allows for rapid fabrication of variable-pitch sub-wavelength hole arrays in metal films for use as transparent electrical contacts, and evaluation of the evanescent and propagating mode coupling to resonances in the active layer.

laser-driven light source↗
DOE OSTI2019

Experimental Evidence of the Lorentz-like Effective Medium Resonance in Semiconductor Hyperbolic Metamaterials using Strong Coupling to Plasmonic Metasurfaces

The Lorentz-like effective medium resonance (LEMR) exhibited by the longitudinal effective permittivity of semiconductor hyperbolic metamaterials (SHMs) has been known for some time. However, direct observation of this resonance proved to be difficult. Here we experimentally demonstrate its existence by strongly coupling SHMs to plasmonic metasurfaces. We consider four strong coupling implementations of SHMs that exhibit different LEMR absorption profiles (both in frequency and strength) to validate our approach.

42 ENGINEERING↗
DOE OSTI2021

Strengths of plasmon satellites in XPS: Real-time cumulant approach

Plasmon satellites observed in x-ray photoemission spectra (XPS) reflect many-body effects beyond the single-electron approximation. However, theoretical calculations are challenging and simplified theories based on electron gas models are not always satisfactory. Here, a cumulant Green’s function approach with a real-time time-dependent density functional theory calculation of the cumulant is described for calculations of these effects, without the need for adjustable parameters. Here, the approach yields good agreement with experimental XPS results, as illustrated for Ge and Al. Corrections due to extrinsic losses and interference are also briefly discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

In situ plasmonic tip preparation and validation techniques for scanning tunneling microscopy

Among the many parts constituting a scanning tunneling microscope, the metallic tip is the component that directly interacts with the specimen and plays a critical role in visualizing the physical quantity of interest. While tip materials such as W and Pt–Ir are commonly used for topographic imaging and their preparation is well-documented, the preparation of plasmonic materials such as Ag for tip-enhanced Raman spectroscopy is relatively less standardized. Furthermore, we present several in situ Ag tip preparation and validation techniques for the microscopist to use depending on their intended application, including atomic resolution imaging, scanning tunneling spectroscopy (STM), and tip-enhanced Raman spectro-microscopy in ultrahigh vacuum. Besides optical applications, these methods are not limited to Ag but also applicable to other STM tip materials.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Concentration of energy inside laser-irradiated gold and silver plasmon nanoparticles in air

We simulated laser-intensity distribution inside spherical gold and silver nanoparticles with radii between 10 and 100 nm, which are exposed to laser radiation at 400, 532, and 800 nm in air, and analyzed the results. The effect of high energy concentration inside illuminated (front) and shadowed (back) hemispheres of gold and silver nanoparticles is established for several nanoparticle sizes and laser wavelengths. The results can be used in nanophotonics of new plasmon devices (concentrators, antennas, etc.) and photon components.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Scattering of electromagnetic pulses on metallic nanospheres with the inclusion of plasmon interference effects

The spectral–angular features of the scattering of electromagnetic pulses with various durations (from quasimonochromatic to ultrashort) on metallic nanoparticles in a dielectric medium have been studied for various parameters of the problem. It has been shown that the character of the interference of contributions from surface plasmons with various multipole orders significantly depends on the scattering angle and is responsible for sharp features in the scattering spectrum of monochromatic radiation. The dependence of the probability and scattering spectrum on the duration of a pulse and the scattering angle has been analyzed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗