114 research outputs found
Light capsules shaped by curvilinear meta-surfaces
We propose a simple yet efficient method for generating in-plane hollow beams
with a nearly-full circular light shell without the contribution of backward
propagating waves. The method relies on modulating the phase in the near field
of a centro-symmetric optical wavefront, such as that from a
high-numericalaperture focused wave field. We illustrate how beam acceleration
may be carried out by using an ultranarrow non-flat meta-surface formed by
engineered plasmonic nanoslits. A mirrorsymmetric, with respect to the optical
axis, circular caustic surface is numerically demonstrated that can be used as
an optical bottle
Influence of copper on the electronic properties of amorphous chalcogenides
We have studied the influence of alloying copper with amorphous arsenic
sulfide on the electronic properties of this material. In our
computer-generated models, copper is found in two-fold near-linear and
four-fold square-planar configurations, which apparently correspond to Cu(I)
and Cu(II) oxidation states. The number of overcoordinated atoms, both arsenic
and sulfur, grows with increasing concentration of copper. Overcoordinated
sulfur is found in trigonal planar configuration, and overcoordinated
(four-fold) arsenic is in tetrahedral configuration. Addition of copper
suppresses the localization of lone-pair electrons on chalcogen atoms, and
localized states at the top of the valence band are due to Cu 3d orbitals.
Evidently, these additional Cu states, which are positioned at the same
energies as the states due to ([As4]-)-([S_3]+) pairs, are responsible for
masking photodarkening in Cu chalcogenides
Low-loss waveguides in ultrafast laser-deposited As(2)S(3) chalcogenide films
This paper was published in Journal of the Optical Society of America B and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/abstract.cfm?URI=josab-20-9-1844. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.A. Zakery, Y. Ruan, A. V. Rode, M. Samoc, and B. Luther-Davie
Optical Nonlinearities in Chalcogenide Glasses and their Applications
Photonics, which uses photons for information and image processing, has been labeled the technology of the 21st century, for which non-linear optical processes provide the key functions of frequency conversion and optical switching. Chalcogenide glass fiber is one of the most promising candidates for use as a non-linear optical medium because of its high optical nonlinearity and long interaction length. Since the chalcogenide glass fibers transmit into the IR, there are numerous potential applications in the civil, medical and military areas. One of the most exciting developments in the future is going to be in the area of rare-earth ion doping of chalcogenide fibers for IR fluorescence emission. The IR light sources, lasers and amplifiers developed using this phenomena will be very useful in civil, medical and military applications. Remote IR spectroscopy and imaging using flexible fibers will be realized for applications. Other future research areas which will inevitably be explored includes non-linear optical properties of these IR glasses. High-speed optical communication requires ultra-fast all-optical processing and switching capabilities. The Kerr non-linearity, an ultrafast optical non-linearity, is often used as the basic switching mechanism. A practical, small device that can be switched ~ 1 pJ energies requires a large Kerr effect with minimal losses (both linear and non-linear). Chalcogenides have a Kerr non-linearity hundred of times larger that silica, making them excellent and unique for ultrafast all-optical devices. Results of non-linearity of chalcogenide glasses indicate the great potential of some of these glasses for all-optical switching and all-optical processing devices
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