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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 1,225 records · Page 68
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Gelation of plasmonic metal oxide nanocrystals by polymer-induced depletion attractions

Significance Self-supported gelation of optically active nanocrystals offers a modular pathway to harness optoelectronic functionality in multiscale materials by directly controlling volume fraction, bonding, and structure during assembly. We combine depletion attractions that emerge from the incorporation of small polymer chains and electrostatic repulsions to induce the gelation of isotropic metal oxide nanocrystals. We develop a theoretical model to assess our experimental fluid-to-gel-phase progression observations. By preventing nanocrystal fusion during network assembly, we achieve gels with a strong near-infrared absorption, reminiscent of the inherent near-infrared localized surface plasmon resonance of the nanocrystal building blocks.

Saez Cabezas, Camila A.↗
DOE OSTI2019

Spatially defined molecular emitters coupled to plasmonic nanoparticle arrays

Significance The precise organization of molecular and functional nanoscale building blocks is a long-standing challenge in nanoscience. In particular, overlapping molecular emission with collective optical excitations at the nanoscale can result in exquisite control over the intensity, wavelength, and direction of emitted light. This work describes how positioning molecules that are components of a crystalline material called metal–organic frameworks (MOFs) around plasmonic nanoparticle arrays can result in strongly enhanced emission at wavelengths determined by the lattice, including the splitting of spectral bands by interference effects that do not require strong lattice–molecule coupling for their interpretation. This hybrid platform provides a framework for both spatially and temporally enhancing the properties of luminescent MOFs.

Liu, Jianxi↗
DOE OSTI2024

Switching of electrochemical selectivity due to plasmonic field-induced dissociation

Electrochemical reactivity is known to be dictated by the structure and composition of the electrocatalyst–electrolyte interface. Here, we show that optically generated electric fields at this interface can influence electrochemical reactivity insofar as to completely switch reaction selectivity. We study an electrocatalyst composed of gold–copper alloy nanoparticles known to be active toward the reduction of CO 2 to CO. However, under the action of highly localized electric fields generated by plasmonic excitation of the gold–copper alloy nanoparticles, water splitting becomes favored at the expense of CO 2 reduction. Real-time time-dependent density functional tight binding calculations indicate that optically generated electric fields promote transient-hole-transfer-driven dissociation of the O─H bond of water preferentially over transient-electron-driven dissociation of the C─O bond of CO 2 . These results highlight the potential of optically generated electric fields for modulating pathways, switching reactivity on/off, and even directing outcomes.

Alcorn, Francis M.↗
DOE OSTI2022

Plasmon spectroscopy for the determination of Ti 3 C 2 T x MXene few layer stacks architecture

Like many 2D materials, numerous properties of MXene multilayers, and especially the most popular one Ti 3 C 2 T x , have been shown to significantly depend on their architecture, i.e. the number of layers and interlayer distance. These structural parameters are thus key elements to be characterized for the analysis of MXene properties. Focusing on valence electron energy-loss spectroscopy (VEELS) as performed in a transmission electron microscope (TEM), and using density functional theory (DFT) simulations, we here analyze the layer dependent large changes in the VEEL spectra of Ti 3 C 2 T x multilayers as a probe of their total thickness, and emphasize the bulk plasmon energy sensitivity to interlayer distance. Together these findings allow to directly quantify the absolute number of layers in a Ti 3 C 2 T x stack up to ~10 nm thickness and give access to interlayer distance modifications with sub-angström sensitivity, evidencing VEELS as a powerful method for the characterization of MXene multilayers on the nanometer scale. We expect these results to be relevant for the study of structure/properties correlations in this class of materials, especially with the development of in situ or environmental TEM experiments.

Materials Science↗
DOE OSTI2017

Antibunching dynamics of plasmonically mediated entanglement generation

Dissipative entanglement generation protocols embrace open quantum system dynamics to generate long-lived entangled states. In this letter, we report that zero-delay anti-bunching in the $g^{(2)}(\tau)$ correlation function is a signature of dissipative entanglement between actively driven quantum emitters coupled to a plasmonic resirvoir. The anti-bunching effect is a universal signature for entangled bi-partite states generated by relaxation to sub-radiant subspaces. We discuss how the anti-bunching can be validated on experimentally feasible timescales by a Hanburry Brown and Twiss interferometer and analyze the entanglement generation robustness with respect to variations in local detunings, system couplings, and driving fields.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Optical detection and storage of entanglement in plasmonically coupled quantum-dot qubits

Recent proposals and advances in quantum simulations, quantum cryptography, and quantum communications substantially rely on quantum entanglement formation. Contrary to the conventional wisdom that dissipation destroys quantum coherence, coupling with a dissipative environment can also generate entanglement. We consider a system composed of two quantum-dot qubits coupled with a common, damped surface plasmon mode; each quantum dot is also coupled to a separate photonic cavity mode. Cavity quantum electrodynamics calculations show that upon optical excitation by a femtosecond laser pulse, entanglement of the quantum-dot excitons occurs, and the time evolution of the g (2) pair correlation function of the cavity photons is an indicator of the entanglement. We also show that the degree of entanglement is conserved during the time evolution of the system. Furthermore, if coupling of the photonic cavity and quantum-dot modes is large enough, the quantum-dot entanglement can be transferred to the cavity modes to increase the overall entanglement lifetime. This latter phenomenon can be viewed as a signature of entangled, long-lived quantum-dot exciton-polariton formation. In conclusion, the preservation of total entanglement in the strong-coupling limit of the cavity-quantum-dot interactions suggests a novel means of entanglement storage and manipulation in high-quality optical cavities.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Strongly Coupled Plasmon and Phonon Polaritons as Seen by Photon and Electron Probes

The ability to control and modify infrared excitations in condensed matter is of both fundamental and applied interest. Here we explore a system supporting low-energy excitations, in particular, mid-infrared localized plasmon modes and phonon polaritons that are tuned to be strongly coupled. We study the coupled modes by using far-field infrared spectroscopy, state-of-the-art monochromated electron energy-loss spectroscopy, numerical simulations, and analytical modeling. Here we demonstrate that the electron probe facilitates a precise characterization of polaritons constituting the coupled system, and enables an active control over the coupling and the resulting sample response both in frequency and space. Although far-field optical spectra can be substantially different from near-field electron energy-loss spectra, we show that a direct comparison is possible via postprocessing and right positioning of the electron beam. The resulting spectra allow us to evaluate the key parameters of the coupled system, such as the coupling strength, which we demonstrate to be probe independent. Our work establishes a rigorous description of the spectral features observed in light- and localized electron-based spectroscopies, which can be extended to the analysis of analogous optical systems with applications in heat management and electromagnetic field concentration or nanofocusing.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Multibeam absolute stimulated Raman scattering and two-plasmon decay

Multibeam absolute instability thresholds for stimulated Raman scattering (SRS) and two-plasmon decay (TPD) are calculated in three dimensions for conditions relevant to direct-drive inertial confinement fusion experiments on the OMEGA laser and at the National Ignition Facility (NIF). Although multibeam effects are found to be significant for both instabilities, SRS is found to have less efficient multibeam coupling than TPD. The results are consistent with the observation of a TPD-dominated regime on the OMEGA laser and a SRS-dominated regime on the NIF despite the single-beam SRS threshold being lower than the single-beam TPD threshold on both facilities. The minimum instability threshold for NIF plasma parameters occurs for SRS near quarter-critical densities with a shared electromagnetic wave propagating along the beam axis.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Nonuniformly Driven Two-Plasmon-Decay Instability in Direct-Drive Implosions

Half-harmonic emission spectra and images taken during directly driven implosions show that the two-plasmon decay (TPD) instability is driven nonuniformly over the target surface and that multibeam effects dominate this instability. The images show a spatially limited extent of the TPD instability. A prominent spectral feature is used to determine the electron temperature in the corona. Near threshold the temperatures agree with one-dimensional hydrodynamic predictions but exceed them by ~10% above the TPD threshold. Two-dimensional hydrodynamic simulations indicate that a significant part (~20%) of the laser intensity must be locally absorbed by the TPD instability (i.e., by collisional damping of the electron plasma waves) to maintain these temperature islands.

Seka, W.↗
DOE OSTI2014

Multiple Beam Two-Plasmon Decay: Linear Threshold to Nonlinear Saturation in Three Dimensions

The linear stability of multiple coherent laser beams with respect to two-plasmon-decay instability in an inhomogeneous plasma in three dimensions has been determined. Cooperation between beams leads to absolute instability of long-wavelength decays, while shorter-wavelength shared waves are shown to saturate convectively. The multibeam, in its absolutely unstable form, has the lowest threshold for most cases considered. Finally, nonlinear calculations using a three-dimensional extended Zakharov model show that Langmuir turbulence created by the absolute instability modifies the convective saturation of the shorter-wavelength modes, which are seen to dominate at late times.

42 ENGINEERING↗
DOE OSTI2016

Two-plasmon decay mitigation in direct-drive inertial-confinement-fusion experiments using multilayer targets

Multilayer direct-drive inertial-confinement-fusion (ICF) targets are shown to significantly reduce two-plasmon-decay (TPD) driven hot-electron production while maintaining high hydrodynamic efficiency. Implosion experiments on the OMEGA Laser used targets with silicon layered between an inner beryllium and outer silicon-doped plastic ablator. A factor of five reduction in hot-electron generation (> 50 keV) was observed in the multilayer targets relative to pure CH targets. Three-dimensional simulations of the TPD driven hot-electron production using a laser-plasma interaction code (LPSE) that includes nonlinear and kinetic effects show excellent agreement with the measurements. As a result, the simulations suggest that the reduction in hot-electron production observed in the multilayer targets is primarily due to increased electron-ion collisional damping.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Suppressing Two-Plasmon Decay with Laser Frequency Detuning

Three-dimensional laser-plasma interaction simulations show that laser frequency detuning by an amount achievable with current laser technology can be used to suppress the two-plasmon decay (TPD) instability and the corresponding hot-electron generation. For the plasma conditions and laser configuration in a direct-drive inertial confinement fusion implosion on the OMEGA laser, the simulations show that ~0.7% laser frequency detuning is sufficient to eliminate TPD-driven hot-electron generation in current experiments. In conclusion, this allows for higher ablation pressures in future implosion designs by using higher laser intensities.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Anomalous Absorption by the Two-Plasmon Decay Instability

Radiation-hydrodynamic simulations of directly driven fusion experiments at the Omega Laser Facility predict absorption accurately when targets are driven at low overlapped laser intensity. Discrepancies appear at increased intensity, however, with higher-than-expected laser absorption on target. Strong correlations with signatures of the two-plasmon decay (TPD) instability—including half-harmonic and hard-x-ray emission—indicate that TPD is responsible for this anomalous absorption. Scattered light data suggest that up to ≈ 30 % of the laser power reaching quarter-critical density can be absorbed locally when the TPD threshold is exceeded. A scaling of absorption versus TPD threshold parameter was empirically determined and validated using the laser–plasma simulation environment code.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Topological Gaseous Plasmon Polariton in Realistic Plasma

Nontrivial topology in bulk matter has been linked with the existence of topologically protected interfacial states. In this work, we show that a gaseous plasmon polariton (GPP), an electromagnetic surface wave existing at the boundary of magnetized plasma and vacuum, has a topological origin that arises from the nontrivial topology of magnetized plasma. Because a gaseous plasma cannot sustain a sharp interface with discontinuous density, one must consider a gradual density falloff with scale length comparable to or longer than the wavelength of the wave. We show that the GPP may be found within a gapped spectrum in present-day laboratory devices, suggesting that platforms are currently available for experimental investigation of topological wave physics in plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Surface plasmon driven near- and midinfrared photoconductivity in ligand-free ITO nanocrystal films

Semiconductor nanocrystals (NCs) offer exciting opportunities to deploy infrared optoelectronic technology in a variety of applications that are off-limits to conventional single-crystalline materials. However, the performance and stability of state-of-the-art NC-based devices strongly depend on the details of the NC surface and its passivating ligands. Here, the authors use indium tin oxide NC films stripped of organic ligands and conformally coated with Al 2 O 3 to show that absorption enabled by infrared localized surface plasmon resonances permit infrared photoconduction. For Au electrodes, these metallic NC films exhibit stable photoconductive performance over months in ambient and under electrical stress.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Multi-scale theory-assisted nano-engineering of plasmonic-organic hybrid electro-optic device performance

Multi-scale (correlated quantum and statistical mechanics) modeling methods have been advanced and employed to guide the improvement of organic electro-optic (OEO) materials, including by analyzing electric field poling induced electro-optic activity in nanoscopic plasmonic-organic hybrid (POH) waveguide devices. The analysis of in-device electro-optic activity emphasizes the importance of considering both the details of intermolecular interactions within organic electro-optic materials and interactions at interfaces between OEO materials and device architectures. Dramatic improvement in electro-optic device performance--including voltage-length performance, bandwidth, energy efficiency, and lower optical losses have been realized. These improvements are critical to applications in telecommunications, computing, sensor technology, and metrology. Multi-scale modeling methods illustrate the complexity of improving the electro-optic activity of organic materials, including the necessity of considering the trade-off between improving poling-induced acentric order through chromophore modification and the reduction of chromophore number density associated with such modification. Computational simulations also emphasize the importance of developing chromophore modifications that serve multiple purposes including matrix hardening for enhanced thermal and photochemical stability, control of matrix dimensionality, influence on material viscoelasticity, improvement of chromophore molecular hyperpolarizability, control of material dielectric permittivity and index of refraction properties, and control of material conductance. Consideration of new device architectures is critical to the implementation of chipscale integration of electronics and photonics and achieving the high bandwidths for applications such as next generation (e.g., 5G) telecommunications.

Engineering↗
DOE OSTI2019

Application of Plasmonic nanoprobes for SERS sensing and imaging of biotargets in plant systems

The knowledge over gene expression dynamics and location in plants is crucial for applications ranging from basic biological research to agricultural biotechnology (e.g., biofuel development). However, current methods cannot provide in vivo dynamic detection of genomic targets in plants. This limitation is due to the complex sample preparation needed by current methods for nucleic acids detection, which disrupt spatial and temporal resolution. We report the development of a unique multimodal method based on plasmonics-active nanoprobes, referred to inverse molecular sensitnels capable of in vivo imaging and biosensing of microRNA biotargets within whole plant using surface-enhanced Raman scattering (SERS) detection. This work lays the foundations for in vivo functional imaging of RNA biotargets in plants with previously unmet spatial and temporal resolution for many applications ranging from agricultural biotechnology to biofuel research.

biofuel↗
DOE OSTI2018

Dynamic thermal emission control with InAs-based plasmonic metasurfaces

Thermal emission from objects tends to be spectrally broadband, unpolarized, and temporally invariant. These common notions are now challenged with the emergence of new nanophotonic structures and concepts that afford on-demand, active manipulation of the thermal emission process. This opens a myriad of new applications in chemistry, health care, thermal management, imaging, sensing, and spectroscopy. Here, we theoretically propose and experimentally demonstrate a new approach to actively tailor thermal emission with a reflective, plasmonic metasurface in which the active material and reflector element are epitaxially grown, high-carrier-mobility InAs layers. Electrical gating induces changes in the charge carrier density of the active InAs layer that are translated into large changes in the optical absorption and thermal emission from metasurface. We demonstrate polarization-dependent and electrically controlled emissivity changes of 3.6%P (6.5% in relative scale) in the mid-infrared spectral range.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗