Search results for "waves"
showing 10 items of 1766 documents
Optical Imaging of Coherent Molecular Rotors
2020
International audience; Short laser pulses are widely used for controlling molecular rotational degrees of freedom and inducing molecular alignment, orientation, unidirectional rotation and other types of coherent rotational motion. To follow the ultra-fast rotational dynamics in real time, several techniques for producing molecular movies have been proposed based on the Coulomb explosion of rotating molecules, or recovering molecular orientation from the angular distribution of high-harmonics. The present work offers and demonstrates a novel non-destructive optical method for direct visualization and recording of movies of coherent rotational dynamics in a molecular gas. The technique is b…
Assessment of a high-resolution central scheme for the solution of the relativistic hydrodynamics equations
2004
We assess the suitability of a recent high-resolution central scheme developed by Kurganov & Tadmor (2000) for the solution of the relativistic hydrodynamics equations. The novelty of this approach relies on the absence of Riemann solvers in the solution procedure. The computations we present are performed in one and two spatial dimensions in Minkowski spacetime. Standard numerical experiments such as shock tubes and the relativistic flat-faced step test are performed. As an astrophysical application the article includes two-dimensional simulations of the propagation of relativistic jets using both Cartesian and cylindrical coordinates. The simulations reported clearly show the capabili…
Mode cleaning in graphene oxide-doped polymeric whispering gallery mode microresonators
2020
The strategy to incorporate graphene oxide (GO) in a composite material offers significant opportunities to realize compact photonic devices, such as saturable absorbers and polarization selective devices. However, the processing of GO-based composites by direct laser writing, which would afford vast patterning and material flexibility in a single step process, has been little addressed. In this work, we investigated the mechanisms underlying a mode cleaning effect in polymeric whispering gallery mode microresonators containing GO, aiming at the development of on-chip integrable photonic devices. We fabricated the microresonators (cavity loaded Q-factor of 20 000 at 1550 nm) in a single ste…
An Example of Ti:LiNbO3 Device Fabrication: The Mach-Zehnder Electrooptical Modulator
1994
Integrated optics on LiNbO3 has already reached a stage of maturity. Several manufacturers are producing standard and custom devices on LiNbO3 such as high speed (up to 20 GHz) phase and intensity modulators, switching matrices, hybrid optical gyroscopes, etc.1. Two techniques are commonly used to fabricate these devices: titanium indiffusion for 1.3 and 1.5 μm wavelength operation and annealed proton exchange (APE) at 0.8 μm, due to its higher power handling capacity.
In-line fiber-optic sensors based on the excitation of surface plasma modes in metal-coated tapered fibers
2001
Abstract Metal-coated tapered fibers are reported as refractive index sensors based on the resonant excitation of surface plasma modes supported by the metal coating. The devices are easy to fabricate and constitute an alternative to metal-coated side-polished fibers and to other sensors made up of bulk components. We report the fabrication and power transmission properties of quasi-circular devices and asymmetric devices. Both sets of devices can be operated as wavelength output sensors, as well as amplitude output sensors. The transmittance of quasi-circular devices is polarization independent and it changes more than 30 dB as a function of external refractive index.
Relaxation of the order-parameter statistics and dynamical confinement
2020
We study the relaxation of the local ferromagnetic order in the quantum Ising chain in a slant field with both longitudinal and transverse components. After preparing the system in a fully polarised state, we analyse the time evolution of the entire probability distribution function (PDF) of the magnetisation within a block of $\ell$ spins. We first analyse the effect of confinement on the gaussification of the PDF for large $\ell$, showing that the melting of initial order is suppressed when the longitudinal field is aligned to initial magnetisation while it is sped up when it is in the opposite direction. Then we study the thermalisation dynamics. In the paramagnetic region, the PDF quick…
The performance of the ATHENA X-ray Integral Field Unit
2018
The X-ray Integral Field Unit (X-IFU) is a next generation microcalorimeter planned for launch onboard the Athena observatory. Operating a matrix of 3840 superconducting Transition Edge Sensors at 90 mK, it will provide unprecedented spectro-imaging capabilities (2.5 eV resolution, for a field of view of 5') in the soft X-ray band (0.2 up to 12 keV), enabling breakthrough science. The definition of the instrument evolved along the phase A study and we present here an overview of its predicted performances and their modeling, illustrating how the design of the X-IFU meets its top-level scientific requirements. This article notably covers the energy resolution, count-rate capability, quantum …
Polarization of SrBi 2 Ta 2 O 9 ceramics at infra‐low frequencies
2009
Dielectric response in the SrBi2Ta2O9 ceramics is studied over a wide range of temperatures at fields up to Emax ≈ 18 kV/cm. Dependence of dielectric permittivity on field intensity is analyzed at different temperatures. A series of polarization loops are obtained at frequencies 0.1 Hz, 1 Hz, and 10 Hz. The hysteresis at switching polarization is displayed by the shape of polarization loops changing with the field amplitude from bi-angles to quasi-saturated loop patterns of a high degree of rectangularity. The ratio of remnant polarization to maximum polarization as function of field amplitude is presented. Thermal behaviour of the coercive field and the half-width of polarization loops is …
Recovery of oil with unsaturated fatty acids and polyphenols from chaenomelessinensis (Thouin) Koehne: Process optimization of pilot-scale subcritica…
2017
The potential effects of three modern extraction technologies (cold-pressing, microwaves and subcritical fluids) on the recovery of oil from Chaenomelessinensis (Thouin) Koehne seeds have been evaluated and compared to those of conventional chemical extraction methods (Soxhlet extraction). This oil contains unsaturated fatty acids and polyphenols. Subcritical fluid extraction (SbFE) provided the highest yield—25.79 g oil/100 g dry seeds—of the three methods. Moreover, the fatty acid composition in the oil samples was analysed using gas chromatography–mass spectrometry. This analysis showed that the percentages of monounsaturated (46.61%), and polyunsaturated fatty acids (42.14%), after appl…
Network Physiology of Cortico–Muscular Interactions
2020
Skeletal muscle activity is continuously modulated across physiologic states to provide coordination, flexibility and responsiveness to body tasks and external inputs. Despite the central role the muscular system plays in facilitating vital body functions, the network of brain-muscle interactions required to control hundreds of muscles and synchronize their activation in relation to distinct physiologic states has not been investigated. Recent approaches have focused on general associations between individual brain rhythms and muscle activation during movement tasks. However, the specific forms of coupling, the functional network of cortico-muscular coordination, and how network structure a…