385 research outputs found
Fabrication of optical planar waveguides in by He-ion implantation
In this paper, planar waveguides produced by He-ion implantation have been demonstrated in undoped and Yb-doped KY(WO/sub 4/)/sub 2/ crystals. The effective refractive indices of guided modes in surface planar waveguides were measured by dark m-line spectroscopy and the refractive index profiles were reconstructed by calculations based on the inverse WKB method. The end-faces of implanted crystals were polished and the waveguiding properties of the obtained planar structures were investigated using a laser diode at 980 nm and a CCD camera
Growth and magnetism of self-organized arrays of Fe(110) wires formed by deposition on kinetically grooved W(110)
Homoepitaxy of W(110) and Mo(110) is performed in a kinetically-limited
regime to yield a nanotemplate in the form of a uniaxial array of hills and
grooves aligned along the [001] direction. The topography and organization of
the grooves were studied with RHEED and STM. The nanofacets, of type {210}, are
tilted 18° away from (110). The lateral period could be varied from 4 to
12nm by tuning the deposition temperature. Magnetic nanowires were formed in
the grooves by deposition of Fe at 150°C on such templates. Fe/W wires
display an easy axis along [001] and a mean blocking temperature Tb=100KComment: Proceedings of ECOSS 2006 (Paris
Tunable magnetic properties of arrays of Fe(110) nanowires grown on kinetically-grooved W(110) self-organized templates
We report a detailed magnetic study of a new type of self-organized nanowires
disclosed briefly previously [B. Borca et al., Appl. Phys. Lett. 90, 142507
(2007)]. The templates, prepared on sapphire wafers in a kinetically-limited
regime, consist of uniaxially-grooved W(110) surfaces, with a lateral period
here tuned to 15nm. Fe deposition leads to the formation of (110) 7 nm-wide
wires located at the bottom of the grooves. The effect of capping layers (Mo,
Pd, Au, Al) and underlayers (Mo, W) on the magnetic anisotropy of the wires was
studied. Significant discrepancies with figures known for thin flat films are
evidenced and discussed in terms of step anisotropy and strain-dependent
surface anisotropy. Demagnetizing coeffcients of cylinders with a triangular
isosceles cross-section have also been calculated, to estimate the contribution
of dipolar anisotropy. Finally, the dependence of magnetic anisotropy with the
interface element was used to tune the blocking temperature of the wires, here
from 50K to 200 K
Periodically rippled graphene: growth and spatially resolved electronic structure
We studied the growth of an epitaxial graphene monolayer on Ru(0001). The
graphene monolayer covers uniformly the Ru substrate over lateral distances
larger than several microns reproducing the structural defects of the Ru
substrate. The graphene is rippled with a periodicity dictated by the
difference in lattice parameter between C and Ru. The theoretical model predict
inhomogeneities in the electronic structure. This is confirmed by measurements
in real space by means of scanning tunnelling spectroscopy. We observe electron
pockets at the higher parts of the ripples.Comment: 5 page
Fabrication of optical planar and channel waveguides in Yb<sup>3+</sup> doped KY(WO<sub>4</sub>)<sub>2</sub> by He-ion implantation
Light ion implantation can be regarded as a universal tool for fabricating low-loss waveguide structures in optically active oxide materials. We have fabricated planar optical waveguides in :(2%) crystals by implanting He+ ions at 1.5 MeV, with doses ranging from 1 to 3x10^16 ions/cm2. An optical barrier with a decreased effective refractive index was created at the end of the ions' tracks, situated approximately 3.5 ÎĽm below the surface. The change in refractive index with respect to the bulk value and its stability to thermal treatment were investigated by dark m-line spectroscopy. Surface channel waveguides were obtained by writing sidewalls into the planar guiding layer by implantation through a slit. The sidewalls were produced by keeping the ion energy fixed and varying the incident angle of implantation. Channel waveguides of 5-ÎĽm width and 4-ÎĽm depth were obtained in the regions between the implanted sidewalls. Beam-propagation parameters were measured by investigating the output profile of end-coupled, fundamental-mode laser light at 980 nm. The results of loss measurements will be presented at the conference
Static-electric-field behavior in negative ion detachment by an intense, high-frequency laser field
Based upon the exact numerical solution of the complex quasienergy problem for a 3-dimensional short-range potential as well as upon analytical evaluations, we demonstrate for any finite frequency ω that the action of an ultra-intense laser field (with electric vector F(ωt)) on a weakly bound atomic system may be described by the cycle-averaging of results for an instantaneous static electric field of strength |F(ωt)|
Focused-ion-beam nano-structured rib channel waveguides in KY(WO<sub>4</sub>)<sub>2</sub> for laser applications
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