Long-Range Fiber Transmission of Optical Vortices

We use specialty fiber (“vortex fiber”), to create and propagate orbital angular momentum states over ~kilometer lengths in telecom band (~1550nm). The spiral phase structure of the vortex beams was confirmed by interference with a Gaussian reference. This result is an important step toward achieving long-range classical and quantum communication links using orbital angular momentum of light.

Restoration of optical objects using regularization

Using the regularization theory for improperly posed problems, we discuss object restoration beyond the diffraction limit in the presence of noise. Only the case of one-dimensional coherent objects is considered. We focus attention n the estimation of the error on the restored objects, and we show that, in most realistic cases, it is at best proportional to an inverse power of

A note on the restoration of optical objects

info:eu-repo/semantics/nonPublished

Layers of generality and types of generalization in pattern activities

Pattern generalization is considered one of the prominent routes for in-troducing students to algebra. However, not all generalizations are al-gebraic. In the use of pattern generalization as a route to algebra, we —teachers and educators— thus have to remain vigilant in order not to confound algebraic generalizations with other forms of dealing with the general. But how to distinguish between algebraic and non-algebraic generalizations? On epistemological and semiotic grounds, in this arti-cle I suggest a characterization of algebraic generalizations. This char-acterization helps to bring about a typology of algebraic and arithmetic generalizations. The typology is illustrated with classroom examples.

Near-field distribution of optical transmission of periodic subwavelength holes in a metal film

Optical transmission of a two-dimensional array of subwavelength holes in a metal film has been numerically studied using a differential method. Transmission spectra have been calculated showing a significant increase of the transmission in certain spectral ranges corresponding to the excitation of the surface polariton Bloch waves on a metal surface with a periodic hole structure. Under the enhanced transmission conditions, the near-field distribution of the transmitted light reveals an intensity enhancement greater than 2 orders of magnitude in localized (similar to 40 nm) spots resulting from the interference of the surface polaritons Bragg scattered by the holes in an array.

Sorption behavior of cationic and anionic dyes from aqueous solution on different types of activated carbons

The effect of dye molecular charges on their adsorption from solution was investigated by using different types of activated carbon adsorbents. Two types of model systems were used representing cationic and anionic dyes. Screening investigations using single point tests were used throughout the study. Cationic dyes, of which Methylene Blue is an example, showed a higher adsorption tendency towards activated carbon over anionic dyes represented by an ate-type reactive compound. Of the number of activated carbons tested, only one of the adsorbents showed an exception to this behavior, and a good relation was observed between Methylene Blue capacity and activated carbon performance. The high capacity of cationic dyes in comparison to anionic dyes was also evident in the results obtained by a preliminary kinetic study carried out on the selected systems. Surface net charge of activated carbon and the nature of attractions between the molecules were suggested to be one of the reasons attributed for this behavior.