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Results for “Optical physics”
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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Light-controlled spintronic device based on hybrid organic–inorganic perovskites
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Strategies for defect-tolerant microconcentrator photovoltaic modules
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POLARBEAR-2: an instrument for CMB polarization measurements
POLARBEAR-2 (PB-2) is a cosmic microwave background (CMB) polarization experiment that will be located in the Atacama highland in Chile at an altitude of 5200 m. Its science goals are to measure the CMB polarization signals originating from both primordial gravitational waves and weak lensing. PB-2 is designed to measure the tensor to scalar ratio, r, with precision σ(r) > 0:01, and the sum of neutrino masses, Σm z , with σ(Σmv) < 90 meV. To achieve these goals, PB-2 will employ 7588 transition-edge sensor bolometers at 95 GHz and 150 GHz, which will be operated at the base temperature of 250 mK. Science observations will begin in 2017.
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.
Electronic structure and dynamics of confined atoms
Confined atomic systems are of great importance owing a multitude of possible applications in various areas of science and technology. Of particular interest are atoms encaged in the C 60 molecule, A@C 60 , since the near-spherical symmetry of C 60 simplifies theoretical studies, and the stability of C 60 renders it amenable to experimental examination. Herein a review of investigations of the electronic structure and dynamics of A@C 60 is presented in this manuscript focusing on developments in the last decade. Addressed mainly are how the confinement affects electronic structure properties such as ionization potentials, localization of atomic electrons, Shannon entropy, correlation effects, relativistic interactions, and others. In the area of dynamics, photoionization and e-A@C 60 scattering are reviewed and summarized, and the major effects of confinement on the dynamical properties, e.g., confinement resonances, hybridization, Wigner time delay, are delineated.
Gold nanoparticles for cancer theranostics — A brief update
Gold nanoparticles (AuNPs) exhibit superior optical and physical properties for more effective treatment of cancer through incorporating both diagnostic and therapeutic functions into one single platform. The ability to passively accumulate on tumor cells provides AuNPs the opportunity to become an attractive contrast agent for X-ray based computed tomography (CT) imaging in vivo. Because of facile surface modification, various size and shape of AuNPs have been extensively functionalized and applied as active nanoprobes and drug carriers for cancer targeted theranostics. Moreover, their capabilities on producing photoacoustic (PA) signals and photothermal effects have been used to image and treat tumor progression, respectively. Furthermore, we review the developments of AuNPs as cancer diagnostics and chemotherapeutic drug vector, summarizing strategies for tumor targeting and their applications in vitro and in vivo.
Generalized proximal smoothing (GPS) for phase retrieval
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Adaptive control of laser-wakefield accelerators driven by mid-IR laser pulses
There has been growing interest both in studying high intensity ultrafast laser plasma interactions with adaptive control systems as well as using long wavelength driver beams. We demonstrate the coherent control of the dynamics of laser-wakefield acceleration driven by ultrashort (~ 100 fs) mid-infrared (~ 3.9 μ m) laser pulses. The critical density at this wavelength is 7.3 × 10 19 cm -3 , which is achievable with an ordinary gas target system. Interactions between mid-infrared laser pulses and such near-critical-density plasma may be beneficial due to much higher absorption of laser energy. In addition, the normalized vector potential of the laser field a 0 increases with longer laser wavelength, lowering the required peak laser intensity to drive non-linear laser-wakefield acceleration. Here, MeV level, collimated electron beams with non-thermal, peaked energy spectra are generated. Optimization of electron beam qualities are realized through adaptive control of the laser wavefront. A genetic algorithm controlling a deformable mirror improves the electron total charge, energy spectra, beam pointing and stability at various plasma density profiles. Particle-in-cell simulations reveal that the optimal wavefront causes an earlier injection on the density up-ramp and thus higher energy gain as well as less filamentation during the interaction, which leads to the improvement in electron beam collimation and energy spectra.
Q-switched and gain-switched Fe:ZnSe lasers tunable over 360–515 µm
We report on room temperature gain-switched and Q-switched Fe:ZnSe lasers tunable over 3.60–5.15 µm pumped by radiation of an 2.94 µm Er:YAG laser. The maximum output energy was measured to be 5 mJ under 15 mJ of pump energy in gain-switched regime. We also demonstrated a mechanically Q-switched regime of oscillation of Fe:ZnSe lasers. This approach could be attractive for the development of high-energy short-pulse solid-state mid-IR systems operating over 3.6–5.2 µm spectral range.
Multi-octave visible to long-wave IR femtosecond continuum generated in Cr:ZnS-GaSe tandem
We report a technique for generation of broad and coherent femtosecond (fs) continua that span several octaves from visible to long-wave IR parts of the spectrum (0.4–18 µm). The approach is based on simultaneous amplification of few-cycle pulses at 2.5 µm central wavelength at 80 MHz repetition rate, and augmentation of their spectrum via three-wave mixing in a tandem arrangement of polycrystalline Cr:ZnS and single crystal GaSe. The obtained average power levels include several mW in the 0.4–0.8 µm visible, 0.23 W in the 0.8–2 µm near-IR, up to 4 W in the 2–3 µm IR, and about 17 mW in the 3–18 µm long-wave IR bands, respectively. High brightness and mutual coherence of all parts of the continuum was confirmed by direct detections of the carrier envelope offset frequency of the master oscillator.