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Vrije Universiteit Brussel

John Edward Sipe

Peter W E Smith

Nathalie Vermeulen

Hugo Jean Arthur Thienpont

Henry Martin Van Driel

Thomas Szkopek

A novel multimode fiber structure with modal propagation characteristics tailored to facilitate the creation of narrowband, high reflectivity, fiber Bragg gratings is disclosed. The fiber structure comprises concentric cylindrical shells of higher and lower refractive index material. A full vector, second order finite element method is used to analyze the proposed multimode fiber structure. Simulations of the modal profiles show that high order modes are localized to particular high refractive index shells. We present the theoretical characterization of the modal propagation constant as a function of inner shell radius, shell separation, and harmonic mode parameter. It is shown that a fiber with a minimum inner shell radius of at least 25&lgr; (where &lgr; is the vacuum wavelength), and a minimum shell separation of at least 10&lgr; provides a reasonable trade off between fiber size and grating performance. A simulation of the multimode fiber grating shows that a grating with a FWHM bandwidth on the order of 10 &lgr; is theoretically possible if optical power is launched strictly into modes with angular harmonic parameter p&equals;1.

Multimode fiber for narrowband bragg gratings

A method and apparatus for generating and controlling the propagation of electrons in a semiconductor material using a plurality of beams of coherent light is disclosed. The direction and magnitude of propagation of the electrons in the semiconductor are controlled by varying the polarization of the coherent beams with respect to the semiconductor material, and in particular the crystallographic axis of the semiconductor material. The electrons are generated and controlled by use of three coherent beams which are related such that the frequency of one of the beams is substantially equal to the sum of the frequencies of the other beams, and the first beam produces substantially the same number of electrons in the semiconductor material that the other beams produce together. A selected region of the semiconductor material is simultaneously irradiated with all of the beams of light. The semiconductor material is at approximately room temperature. Holes are also generated and propagate in a direction opposite to the direction of propagation of the electrons.

Method and apparatus for controlling propagation of electrical charges

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Toronto, Canada

John Edward Sipe