1,721,236 research outputs found
(WO2017021888) OPTICAL DEVICE FOR DEMULTIPLEXING AND MULTIPLEXING A PLURALITY OF CHANNELS WITH DIFFERENT WAVELENGTH AND DIFFERENT ORBITAL ANGULAR MOMENTUM AND OPTICAL COMMUNICATION SYSTEM THEREOF
No full textNear-field numerical analysis of surface plasmon polariton propagation on metallic gratings
No full textGrating-coupled surface plasmon resonance in conical mounting with polarization modulation
No full textA grating-coupled surface plasmon resonance (GCSPR) technique based on polarization modulation in conical mounting is presented. A metallic grating is azimuthally rotated to support double-surface plasmon polariton excitation and exploit the consequent sensitivity enhancement. Corresponding to the resonance polar angle, a polarization scan of incident light is performed, and reflectivity data are collected before and after functionalization with a dodecanethiol self-assembled monolayer. The output signal exhibits a harmonic dependence on polarization, and the phase term is used as a parameter for sensing. This technique offers the possibility of designing extremely compact, fast, and cheap high-resolution plasmonic sensors based on GCSPR. (C) 2012 Optical Society of Americ
Dechanneling by misfit dislocations in III-V semiconductor heterostructures
No full textThis work reports on the use of the dechanneling technique for the determination of the misfit dislocation distribution at the interface between mismatched III-V semiconductor heterostructures grown on (001) substrates. Planar channeling is employed because of the higher sensitivity with respect to the axial case. For low misfit heterostructures, dislocations are oriented along the [110] and [110BAR] and the depth distribution is nearly planar and close to the chemical interface. We show that, for this kind of structure, dechanneling measurements allow one to determine the dislocation densities along the two quoted directions. This is done by using a fitting procedure based on a numerical simulation program of the RBS-channeling spectra. As a result of this procedure, an estimation of the dislocation distribution thickness can also be obtained, besides the ratio of the energy loss under channeling conditions to that under non-channeling conditions. Experimental data concerning a set of InxGa1-xAs/GaAs single layer samples having different thicknesses and indium concentrations are presented and discussed in the framework of this model. The dechanneling probability due to the misfit dislocations is obtained from the RBS-channeling spectra at several beam energies for all the samples. In some cases we note two distinct dechanneling probabilities for the two {110} channeling planes perpendicular to the interface. In light of the dechanneling cross section properties, this fact reflects the difference between the dislocation densities in the two directions
Design of a free-space optical link based on multipole-phase division multiplexing
Full text linkIn recent decades, control of the spatial structure of electromagnetic waves has boosted the research of new modulation formats for telecommunications and quantum applications. In particular, the exploitation of orthogonal spatial modes as distinct information carriers in the so-called spatial-division multiplexing has been dominated so far by beams carrying orbital angular momentum (OAM). However, practical solutions based on OAM-mode multiplexing still suffer from critical issues related, for instance, to efficient generation and long distance transmissions in free space. In a more general approach to wavefront propagation, we have recently introduced an innovative framework based on beams with harmonic phases characterized by multipole structures devoid of phase singularities, referred to as multipole-phase beams. This new paradigm offers efficient multiplexing and sorting in a full-optical and compact architecture based on conformal transformations, promising, moreover, to overcome the limits of previous solutions in free-space transmissions. The generalization to high orders of multipole phase is considered here, investigating a possible layout for a free space optical link. Numerical simulations are performed and discussed to validate the theory and show the potentialities of this new framework for telecommunications, both at the classical and single photon regimes
Propagation of grating-coupled surface plasmon polaritons and cosine-Gauss beam generation
No full textIon-beam analysis of mismatched epitaxial heterostructures
No full textThe structural characterization of mismatched epitaxial heterostructures requires at least the determination of the strain and of the dislocation density. In this paper it is shown that ion-channeling is a very suitable technique for measuring both of these properties. In particular an improved technique for measuring the absolute angular distance between any crystal direction is presented. It is shown that in the case of single layer heterostructures the achieved precision is comparable to or better than that of double crystal X-ray diffraction. Moreover by computing the lattice distortion caused by a misfit dislocation the dechanneling cross section and its dependence from the relative orientation of the channeling and the dislocation directions have been evaluated. The application of these techniques for studying the mechanisms of strain relaxation in the InxGa1-xAs/GaAs system is presented
Interface lithography: a hybrid lithographic approach for the fabrication of patterns embedded in three-dimensional structures
No full textDechanneling cross-section for misfit dislocations
No full textThis work reports on the use of the dechanneling technique for the determination of the misfit dislocation distribution at the interface between mismatched III-V semiconductor heterostructures grown on (001) substrates. In this case the dislocations are oriented along the [110] and [110BAR] and the depth distribution is nearly planar and close to the chemical interface. The displacement field caused by one misfit dislocation is calculated in the frame of the linear elasticity theory. An analytical treatment of the dechanneling cross section dependence on both the dislocation line and Burgers vector orientation and on the beam direction in the channeling plane is performed within the Quere model. It is shown that (110) planar channeling is most sensitive to the dislocation orientation. Experimental data concerning a set of InxGa1-xAs/GaAs single layer samples are presented and analyzed. The two {110} planes perpendicular to the interface show distinct dechanneling probabilities. In the light of the dechanneling cross section properties this fact reflects the difference between the dislocation densities in the two directions. The obtained dislocation densities are in agreement with those derived indirectly from strain measurements. It is shown that the sensitivity of the dechanneling technique is of the order of 10(4) dislocation lines cm-1
Compact sorting of optical vortices by means of diffractive transformation optics
No full textThe orbital angular momentum (OAM) of light has recently attracted a growing interest as a new degree of freedom in order to increase the information capacity of today's optical networks, both for free-space and optical fiber transmission. Here we present our work of design, fabrication, and optical characterization of diffractive optical elements for compact OAM mode division demultiplexing based on optical transformations. Samples have been fabricated with 3D high-resolution electron beam lithography on a polymethylmethacrylate resist layer spun over a glass substrate. Their high compactness and efficiency make these optical devices promising for integration into next-generation platforms for OAM modes processing in telecom applications
- …
