Search results for "Toe"
showing 10 items of 3824 documents
Transition-edge microcalorimeters for X-ray space applications
2000
Abstract In an European Space Agency funded research project, our goal is to develop microbolometer technology for X-ray and far-infrared detection for ESA's future scientific missions. We report results on the X-ray calorimeter, which is based on the superconducting transition of the Ti/Au thermometer strip at about 200 mK. Incident X-rays heat up a Bi absorber, deposited on top of the 400 μm ×400 μm thermometer. The temperature rise of the absorber is measured as a change of the thermometer current with a SQUID operating at 1 K.
Field-free permanent molecular planar alignment
2009
We show the existence of a permanent molecular planar alignment in field-free conditions. We present different control strategies using shaped laser pulses to reach this state. The strategies are robust with respect to the temperature and can be implemented with the state of the art technology. They can be applied not only to linear molecules but also to symmetric or asymmetric top molecules along the most polarizable molecular axis. We propose potential applications of this planar alignment such as the increase of the adsorption on a surface.
To the theory of high-power gyrotrons with uptapered resonators
2010
In high-power gyrotrons it is desirable to combine an optimal resonator length with the optimal value of the resonator quality factor. In resonators with the constant radius of the central part, the possibilities of this combination are limited because the quality factor of the resonator sharply increases with its length. Therefore the attempts to increase the length for maximizing the efficiency leads to such increase in the quality factor which makes the optimal current too small. Resonators with slightly uptapered profiles offer more flexibility in this regard. In such resonators, one can separate optimization of the interaction length from optimization of the quality factor because the …
Review on up/down conversion materials for solar cell application
2012
The present paper reviews the methods of photon up- and down conversion strategies for improving the efficiency of solar cells. Photons with a lower energy than the band gap will be lost in a normal solar cell. The principle of the up conversion technique is that two or more photons are converted into a photon with energy higher than the band gap energy. High energy photons will lose the energy above the band gap energy limit. Down conversion is a process where a high energy photon is converted into several lower energy photons with energies above the band gap. A description is given of the most common methods and materials for these conversions resulting in higher solar cell efficiencies.
Photonic transfer through subwavelength optical waveguides
1998
Optical tunneling effect through dielectric junctions with subwavelength transverse sizes has been demonstrated some years ago. In this letter, we demonstrate how similar effects can be exploited to perform photonic transfer through a subwavelength optical wave guide (SOW) by structuring its optical index along the direction of propagation. The optical transmittance of the SOW is computed self-consistently in direct space through the numerical solution of a Dyson equation. We apply this scheme to investigate the optical properties of different SOW architectures. Even under total internal reflection, in which the light is coupled to the SOW by an evanescent mode, an efficient optical transfe…
Plasmon-driven Bessel beams
2012
We report on subwavelength diffraction-free beams with grazing propagation in metal-dielectric devices. The nondiffracting beams are resonantly transmitted through the nanostructured medium leading to light confinement and wave amplification around the beam axis.
Néel Vector Induced Manipulation of Valence States in the Collinear Antiferromagnet Mn 2 Au
2020
The coupling of real and momentum space is utilized to tailor electronic properties of the collinear metallic antiferromagnet Mn2Au by aligning the real space Neel vector indicating the direction o...
Metal valence states inEu0.7NbO3,EuNbO3,andEu2Nb5O9by TB-LMTO-ASA band-structure calculations and resonant photoemission spectroscopy
1998
The electronic structures of ${\mathrm{Eu}}_{2}{\mathrm{Nb}}_{5}{\mathrm{O}}_{9},$ ${\mathrm{EuNbO}}_{3},$ and ${\mathrm{Eu}}_{0.7}{\mathrm{NbO}}_{3}$ have been investigated by photoemission and total-yield spectroscopy with synchrotron radiation, and in the case of ${\mathrm{Eu}}_{2}{\mathrm{Nb}}_{5}{\mathrm{O}}_{9}$ by tight-binding linear muffin-tin orbital (LMTO) band-structure calculations. A central question for reduced europium niobates is that of the valence of Eu and Nb. Both europium and niobium atoms can appear in different valence states so that various electronic configurations in the title compounds are possible. For this reason, the valence band was studied by the resonant Eu…
Dynamical Processes in Open Quantum Systems from a TDDFT Perspective: Resonances and Electron Photoemission
2015
We present a review of different computational methods to describe time-dependent phenomena in open quantum systems and their extension to a density-functional framework. We focus the discussion on electron emission processes in atoms and molecules addressing excited-state lifetimes and dissipative processes. Initially we analyze the concept of an electronic resonance, a central concept in spectroscopy associated with a metastable state from which an electron eventually escapes (electronic lifetime). Resonances play a fundamental role in many time-dependent molecular phenomena but can be rationalized from a time-independent context in terms of scattering states. We introduce the method of c…
Metacoatings for wavelength-scale, high-numerical-aperture plano–concave focusing lenses
2016
We design plano–concave silicon lenses with coupled gradient-index plasmonic metacoatings for ultrawide apertured focusing utilizing a reduced region of ∼20λ2. The anomalous refraction induced in the planar input side of the lens and in the boundary of the wavelength-scale focal region boosts the curvature of the emerging wavefront, thus significantly enhancing the resolution of the tightly focused optical wave. The formation of a light tongue with dimensions approaching those of the concave opening is here evidenced. This scheme is expected to have potential applications in optical trapping and detection.