Cobalt ferrite thin films have been elaborated by pulsed laser ablation of a CoFe
2 metallic target on Si (100) substrates. The films were deposited at low temperature (300 °C) in various pressures ...of two different reactive atmospheres (O
2/N
2, 20:80 and O
2). We present the influence of the nature of the reactive gas and of the deposition pressure on the crystallisation. It has been shown that a strong (111) preferential orientation is obtained for intermediate pressures of the O
2/N
2 reactive gas. The degree of orientation is higher for the O
2/N
2 mixture than for pure O
2. This behaviour is explained in terms of kinetic energy of the deposited species.
ABSTRACT
The definition and optimization studies for the Gaia satellite spectrograph, the ‘radial velocity spectrometer’ (RVS), converged in late 2002 with the adoption of the instrument baseline. ...This paper reviews the characteristics of the selected configuration and presents its expected performance. The RVS is a 2.0 × 1.6 degree integral field spectrograph, dispersing the light of all sources entering its field of view with a resolving power R=λ/Δλ= 11 500 over the wavelength range 848, 874 nm. The RVS will continuously and repeatedly scan the sky during the 5‐yr Gaia mission. On average, each source will be observed 102 times over this period. The RVS will collect the spectra of about 100–150 million stars up to magnitude V≃ 17–18. At the end of the mission, the RVS will provide radial velocities with precisions of ∼2 km s−1 at V= 15 and ∼15–20 km s−1 at V= 17, for a solar‐metallicity G5 dwarf. The RVS will also provide rotational velocities, with precisions (at the end of the mission) for late‐type stars of σvsin i≃ 5 km s−1 at V≃ 15 as well as atmospheric parameters up to V≃ 14–15. The individual abundances of elements such as silicon and magnesium, vital for the understanding of Galactic evolution, will be obtained up to V≃ 12–13. Finally, the presence of the 862.0‐nm diffuse interstellar band (DIB) in the RVS wavelength range will make it possible to derive the three‐dimensional structure of the interstellar reddening.
X-shooter is the first 2nd generation instrument of the ESO Very Large Telescope (VLT). It is a very efficient, single-target, intermediate-resolution spectrograph that was installed at the ...Cassegrain focus of UT2 in 2009. The instrument covers, in a single exposure, the spectral range from 300 to 2500 nm. It is designed to maximize the sensitivity in this spectral range through dichroic splitting in three arms with optimized optics, coatings, dispersive elements and detectors. It operates at intermediate spectral resolution (R ~ 4000−17 000, depending on wavelength and slit width) with fixed échelle spectral format (prism cross-dispersers) in the three arms. It includes a 1.8″ × 4″ integral field unit as an alternative to the 11′′ long slits. A dedicated data reduction package delivers fully calibrated two-dimensional and extracted spectra over the full wavelength range. We describe the main characteristics of the instrument and present its performance as measured during commissioning, science verification and the first months of science operations.
We demonstrate the patterning of the quadratic non-linear optical (QNLO) properties in a photopolymerizable resin doped with push–pull chromophores. Advantage is taken of the crosslinking process to ...perform the patterning directly. QNLO gratings with a period of 8.5
μm have been achieved over areas of a few cm
2. This spacing is comparable to the typical visible and near infrared coherence lengths in this material and is therefore suitable for the elaboration of quasi-phase matched waveguides. An accurate characterization of the QNLO gratings has been performed using a high spatial resolution second harmonic generation microscope with a femtosecond laser source.
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