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Results for “WAVELENGTH”

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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Effects of Laser Energy and Wavelength on the Analysis of LiFePO4 Using Laser Assisted Atom Probe Tomography

The effects of laser wavelength (355 nm and 532 nm) and laser pulse energy on the quantitative accuracy of atom probe tomography (APT) examinations of LiFePO4 (LFP) are considered. A systematic investigation of ultraviolet (UV, 355 nm) and green (532 nm) laser assisted APT of LFP has revealed distinctly different behaviors. With the use of UV laser the major issue was identified as the preferential loss of oxygen (up to 10 at. %) while other elements (Li, Fe and P) were observed to be close to nominal ratios. Lowering the laser energy per pulse to 1 pJ increased the observed oxygen concentration to near its correct stoichiometry and was well correlated with systematically higher concentrations of 16O2+ ions. This observation supports the premise that lower laser energies lead to a higher probability of oxygen molecule ionization. Conversely, at higher laser energies the resultant lower effective electric field reduces the probability of oxygen molecule ionization. Green laser assisted field evaporation led to the selective loss of Li (~50% deficiency) and correct ratios of the remaining elements, including the oxygen concentration. The loss of Li is explained by selective dc evaporation of lithium between laser pulses and relatively negligible oxygen loss as neutrals during green-laser pulsing. Lastly, plotting of multihit events on a Saxey plot for the straight-flight path data (green laser only) revealed a surprising dynamic recombination process for some molecular ions mid-flight.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2014

Development and operation of a high-throughput accurate-wavelength lens-based spectrometer

A high-throughput spectrometer for the 400–820 nm wavelength range has been developed for charge exchange recombination spectroscopy or general spectroscopy. A large 2160 mm{sup −1} grating is matched with fast f/1.8 200 mm lenses, which provide stigmatic imaging. A precision optical encoder measures the grating angle with an accuracy ≤0.075 arc sec. A high quantum efficiency low-etaloning CCD detector allows operation at longer wavelengths. A patch panel allows input fibers to interface with interchangeable fiber holders that attach to a kinematic mount at the entrance slit. Computer-controlled hardware allows automated control of wavelength, timing, f-number, automated data collection, and wavelength calibration.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Emittance-Exchange-Based High Harmonic Generation Scheme for a Short-Wavelength Free Electron Laser

Generation of short-wavelength radiation by a free-electron laser using up-frequency conversion of an electron bunch density modulation is currently an area of active research. We propose a new scheme for producing the longitudinal electron bunch density modulation similar to the recently proposed echo-enabled harmonic generation but based on an emittance exchange beam line and a multislit mask. Beam line analysis and start-to-end simulation are presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Wavelength control and monitor for dense wavelength division multiplexing (DWDM) silicon photonic receiver

Techniques and circuitry for wavelength monitor and control are disclosed herein. The disclosed wavelength monitor and control circuitry and techniques are designed to realize a multi-channel DWDM optical link by using a photonic receiver that dynamically adjusts resonant wavelengths of the microring drop filter (MDF), as needed. The wavelength monitor and control circuitry can monitor and control the resonant wavelengths of multiple MDFs for a DWDM silicon photonics receiver with minimum power and area overhead. In an embodiment, circuitry for an optical receiver comprises an MDF having resonant wavelength for multiple DWDM channels, and circuitry to control and monitor the resonant wavelength of the MDF in real-time and in manner that compensates for deviation between actual resonant wavelength of the MDF and the incident optical wavelength of the MDF.

Huang, Tsung Ching↗
DOE OSTI2015

Compact silicon photonic wavelength-tunable laser diode with ultra-wide wavelength tuning range

We present a wavelength-tunable laser diode with a 99-nm-wide wavelength tuning range. It has a compact wavelength-tunable filter with high wavelength selectivity fabricated using silicon photonics technology. The silicon photonic wavelength-tunable filter with wide wavelength tuning range was realized using two ring resonators and an asymmetric Mach-Zehnder interferometer. The wavelength-tunable laser diode fabricated by butt-joining a silicon photonic filter and semiconductor optical amplifier shows stable single-mode operation over a wide wavelength range.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Modal interactions between a large-wavelength inclined interface and small-wavelength multimode perturbations in a Richtmyer-Meshkov instability

The interaction of a small-wavelength multimodal perturbation with a large-wavelength inclined interface perturbation is investigated for the reshocked Richtmyer-Meshkov instability using three-dimensional simulations. The ares code, developed at Lawrence Livermore National Laboratory, was used for these simulations and a detailed comparison of simulation results and experiments performed at the Georgia Tech Shock Tube facility is presented first for code validation. Simulation results are presented for four cases that vary in large-wavelength perturbation amplitude and the presence of secondary small-wavelength multimode perturbations. Previously developed measures of mixing and turbulence quantities are presented that highlight the large variation in perturbation length scales created by the inclined interface and the multimode complex perturbation. Measures are developed for entrainment, and turbulence anisotropy that help to identify the effects of and competition between each perturbations type. It is shown through multiple measures that before reshock the flow processes a distinct memory of the initial conditions that is present in both large-scale-driven entrainment measures and small-scale-driven mixing measures. After reshock the flow develops to a turbulentlike state that retains a memory of high-amplitude but not low-amplitude large-wavelength perturbations. As a result, it is also shown that the high-amplitude large-wavelength perturbation is capable of producing small-scale mixing and turbulent features similar to the small-wavelength multimode perturbations.

42 ENGINEERING↗
DOE OSTI2021

Entanglement Enabled Intensity Interferometry of different wavelengths of light

Highlights: • We use quantum entanglement to erase the color of photons for a new imaging method. • Can achieve higher resolution imaging by accessing hidden phase information. • We detail practical experimental designs to implement our theoretical protocols. We propose methods to perform intensity interferometry of photons having two different wavelengths. Distinguishable particles typically cannot interfere with each other, but we overcome that obstacle by processing the particles via entanglement and projection so that they lead to the same final state at the detection apparatus. Specifically, we discuss how quasi-phase-matched nonlinear crystals can be used to convert a quantum superposition of light of different wavelengths onto a common wavelength, while preserving the phase information essential for their meaningful interference. We thereby gain access to a host of new observables, which can probe subtle frequency correlations and entanglement. Further, we generalize the van Cittert–Zernike formula for the intensity interferometry of extended sources, demonstrate how our proposal supports enhanced resolution of sources with different spectral character, and suggest potential applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

A dual wavelength imaging system for plasma-surface interaction studies on the National Spherical Torus Experiment Upgrade

A two-channel spectral imaging system based on a charge injection device radiation-hardened intensified camera was built for studies of plasma-surface interactions on divertor plasma facing components in the National Spherical Torus Experiment Upgrade (NSTX-U) tokamak. By means of commercially available mechanically referenced optical components, the two-wavelength setup images the light from the plasma, relayed by a fiber optic bundle, at two different wavelengths side-by-side on the same detector. Remotely controlled filter wheels are used for narrow bandpass and neutral density filters on each optical path allowing for simultaneous imaging of emission at wavelengths differing in brightness up to 3 orders of magnitude. Applications on NSTX-U will include the measurement of impurity influxes in the lower divertor strike point region and the imaging of plasma-material interaction on the head of the surface analysis probe MAPP (Material Analysis and Particle Probe). The diagnostic setup and initial results from its application on the lithium tokamak experiment are presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2010

FERMI LARGE AREA TELESCOPE AND MULTI-WAVELENGTH OBSERVATIONS OF THE FLARING ACTIVITY OF PKS 1510-089 BETWEEN 2008 SEPTEMBER AND 2009 JUNE

We report on the multi-wavelength observations of PKS 1510-089 (a flat spectrum radio quasar (FSRQ) at z = 0.361) during its high activity period between 2008 September and 2009 June. During this 11 month period, the source was characterized by a complex variability at optical, UV, and {gamma}-ray bands, on timescales down to 6-12 hr. The brightest {gamma}-ray isotropic luminosity, recorded on 2009 March 26, was {approx_equal}2 x 10{sup 48} erg s{sup -1}. The spectrum in the Fermi Large Area Telescope energy range shows a mild curvature described well by a log-parabolic law, and can be understood as due to the Klein-Nishina effect. The {gamma}-ray flux has a complex correlation with the other wavelengths. There is no correlation at all with the X-ray band, a weak correlation with the UV, and a significant correlation with the optical flux. The {gamma}-ray flux seems to lead the optical one by about 13 days. From the UV photometry, we estimated a black hole mass of {approx_equal}5.4 x 10{sup 8} M{sub sun} and an accretion rate of {approx_equal}0.5 M{sub sun} yr{sup -1}. Although the power in the thermal and non-thermal outputs is smaller compared to the very luminous and distant FSRQs, PKS 1510-089 exhibits a quite large Compton dominance and a prominent big blue bump (BBB) as observed in the most powerful {gamma}-ray quasars. The BBB was still prominent during the historical maximum optical state in 2009 May, but the optical/UV spectral index was softer than in the quiescent state. This seems to indicate that the BBB was not completely dominated by the synchrotron emission during the highest optical state. We model the broadband spectrum assuming a leptonic scenario in which the inverse Compton emission is dominated by the scattering of soft photons produced externally to the jet. The resulting model-dependent jet energetic content is compatible with a scenario in which the jet is powered by the accretion disk, with a total efficiency within the Kerr black hole limit.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Excitation wavelength dependent photon anti-bunching/bunching from single quantum dots near gold nanostructures

Here, we aim to investigate the change in photon emission statistics of single CdSe/CdS core/shell quantum dots (QDs) on dielectric modified gold nanoparticle (NP) substrates as a function of the excitation wavelength. Photons emitted from single QDs are typically “anti-bunched” and are independent of the excitation wavelength. However, when QDs are coupled to plasmonic substrates, even at the low excitation power regime, we observed a significant change in photoluminescence emission behavior of single QDs; i.e. the emission transformed from incomplete photon anti-bunched to bunched when the excitation was changed from “off” to “on” plasmon resonance. Theoretical studies based on electrodynamics modeling suggested that for the QD–Au NP system, the quantum yield of single excitons decreases while that of biexcitons increases. In addition, when excited at the “on” resonance condition, the absorption is highly enhanced, resulting in an increased population of higher order excitons of the QDs. The higher order exciton emission was directly observed as an additional peak appeared at the blue side of the exciton peak of single QDs. The combined effect of the change in quantum yield and the increase in the absorption cross-section switches the photons emitted by single QDs from anti-bunched to bunched. These results provided direct evidence that not only the plasmonic nanostructures but also the excitation wavelength can effectively control the photon emission statistics of single QDs in the hybrid metal–semiconductor system. Manipulating the multiexciton–plasmon interaction in a hybrid complex like this could possibly open up new doors for applications such as entangled photon pair generation and plasmon-enhanced optoelectronic devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Giant optical second- and third-order nonlinearities at a telecom wavelength

A material platform that excels in both optical second- and third-order nonlinearities at a telecom wavelength is theoretically and experimentally demonstrated. In this TiN-based coupled metallic quantum well structure, electronic subbands are engineered to support doubly resonant inter-subband transitions for an exceptionally high second-order nonlinearity and provide single-photon transitions for a remarkable third-order nonlinearity within the 1400–1600 nm bandwidth. The second-order susceptibility χ (2) reaches 2840 pm/V at 1440 nm, while the Kerr coefficient n 2 arrives at 2.8 × 10 −10 cm 2 /W at 1460 nm. The achievement of simultaneous strong second- and third-order nonlinearities in one material at a telecom wavelength creates opportunities for multi-functional advanced applications in the field of nonlinear optics.

Chen, Ching-Fu (ORCID:0000000262510722)↗
DOE OSTI2016

Anomalous behavior in temporal evolution of ripple wavelength under medium energy Ar{sup +}-ion bombardment on Si: A case of initial wavelength selection

We have studied the early stage dynamics of ripple patterns on Si surfaces, in the fluence range of 1–3 × 10{sup 18} ions cm{sup −2}, as induced by medium energy Ar{sup +}-ion irradiation at room temperature. Under our experimental conditions, the ripple evolution is found to be in the linear regime, while a clear decreasing trend in the ripple wavelength is observed up to a certain time (fluence). Numerical simulations of a continuum model of ion-sputtered surfaces suggest that this anomalous behavior is due to the relaxation of the surface features of the experimental pristine surface during the initial stage of pattern formation. The observation of this hitherto unobserved behavior of the ripple wavelength seems to have been enabled by the use of medium energy ions, where the ripple wavelengths are found to be order(s) of magnitude larger than those at lower ion energies.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Comprehensive Experimental and Computational Spectroscopic Study of Hexacyanoferrate Complexes in Water: From Infrared to X-ray Wavelengths

We present a joint experimental and computational study of the hexacyanoferrate aqueous complexes at equilibrium in the 250 meV to 7.15 keV regime. The experiments include the vibrational spectroscopy of the cyanide ligands, the valence electronic absorption spectra and Fe 1s core hole spectra using X-ray absorption and emission techniques. These experiments are accompanied by density functional theory (DFT) based quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations and spectroscopy calculations of the experiments spanning the IR to X-ray wavelengths. Our simulations, including explicit solvent effects, across this large energy window allows for a systematic comparison of vibrational, valence electronic and core-level spectra. The analysis reveals how the local solvation environment influences the geometric and electronic structure and impacts the line shape and intensity of the observed spectral features in the infrared, optical and X-ray wavelengths.

Ross, Matthew↗
DOE OSTI2012

Triple-wavelength, narrowband Mg/SiC multilayers with corrosion barriers and high peak reflectance in the 25-80 nm wavelength region

We have developed new, corrosion-resistant Mg/SiC multilayer coatings which can be used to efficiently and simultaneously reflect extreme ultraviolet (EUV) radiation in single or multiple narrow bands centered at wavelengths in the spectral region from 25 to 80 nm. Corrosion mitigation is achieved through the use of partially amorphous Al-Mg thin layers. Three different multilayer design concepts were developed and deposited by magnetron sputtering and the reflectance was measured at near-normal incidence in a broad spectral range. Unprotected Mg/SiC multilayers were also deposited and measured for comparison. They were shown to efficiently reflect radiation at a wavelength of 76.9 nm with a peak reflectance of 40.6% at near-normal incidence, the highest experimental reflectance reported at this wavelength for a narrowband coating. The demonstration of multilayer coatings with corrosion resistance and multiplewavelength EUV performance is of great interest in the development of mirrors for space-borne solar physics telescopes and other applications requiring long-lasting coatings with narrowband response in multiple emission lines across the EUV range.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

A multi-wavelength, high-contrast contact radiography system for the study of low-density aerogel foams

A multi wavelength, high contrast contact radiography system has been developed to characterize density variations in ultralow density aerogel foams. These foams are used to generate a ramped pressure drive in materials strength experiments at the National Ignition Facility (NIF) and require precision characterization in order to reduce errors in measurements. Here, the system was used to characterize density variations in carbon and silicon based aerogels to ~10.3% accuracy with ~30 μm spatial resolution. The system description, performance and measurement results collected using a 17.8 mg/cc carbon based JX–6 (C 20 H 30 ) aerogel are discussed in this paper.

42 ENGINEERING↗
DOE OSTI2011

Characterization of Zone Plate Properties using Monochromatic Synchrotron Radiation in the 2 to 20 nm Wavelength Range

A zone plate composed of Mo zones having 4 mm outermost zone diameter, 100 nm outermost zone width, and supported on a silicon nitride membrane was characterized using monochromatic synchrotron radiation in the 2 to 20 nm wavelength range. The zero and first order efficiencies were measured and compared to ab initio calculations that account for the optical properties of the materials, the width and shape of the zones, and multiple-layer thin-film effects. It is shown that the thicknesses of the Mo zones and the membrane and the ratio of the zone width to zone period can be independently determined from the measured diffraction efficiencies in the zero and first orders and that the computational code can be used to reliably design zone plates that are optimized for applications such as solar irradiance monitors in the extreme ultraviolet region.

36 MATERIALS SCIENCE↗