Abstract: A system for conversion or amplification using quasi-phase matched nonlinear optical wave-mixing comprises a first radiation source for providing a pump radiation beam, a second radiation source for providing a signal radiation beam, and a bent structure for receiving the pump radiation beam and the signal radiation beam. The radiation propagation portion of the bent structure is made of a uniform nonlinear optical material and the radiation propagation portion comprises a dimension taking into account the spatial variation of the nonlinear optical susceptibility along the radiation propagation portion as experienced by radiation travelling along the bent structure for obtaining quasi-phase matched nonlinear optical wave-mixing in the radiation propagation portion. The dimension thereby is substantially inverse proportional with the linear phase mismatch for the nonlinear optical process.

Abstract: A system for conversion or amplification using quasi-phase matched nonlinear optical wave-mixing comprises a first radiation source for providing a pump radiation beam, a second radiation source for providing a signal radiation beam, and a bent structure for receiving the pump radiation beam and the signal radiation beam. The radiation propagation portion of the bent structure is made of a uniform nonlinear optical material and the radiation propagation portion comprises a dimension taking into account the spatial variation of the nonlinear optical susceptibility along the radiation propagation portion as experienced by radiation travelling along the bent structure for obtaining quasi-phase matched nonlinear optical wave-mixing in the radiation propagation portion. The dimension thereby is substantially inverse proportional with the linear phase mismatch for the nonlinear optical process.

Abstract: A system for conversion or amplification using quasi-phase matched four-wave-mixing includes a first radiation source for providing a pump radiation beam, a second radiation source for providing a signal radiation beam, and a bent structure for receiving the pump radiation beam and the signal radiation beam. The radiation propagation portion of the bent structure is made of a uniform Raman-active or uniform Kerr-nonlinear material and the radiation propagation portion comprises a dimension taking into account the spatial variation of the Raman susceptibility or Kerr susceptibility along the radiation propagation portion as experienced by radiation travelling along the bent structure for obtaining quasi-phase-matched four-wave-mixing in the radiation propagation portion. The dimension thereby is substantially inverse proportional with the linear phase mismatch for four-wave-mixing.

Abstract: A system for conversion or amplification using quasi-phase matched four-wave-mixing includes a first radiation source for providing a pump radiation beam, a second radiation source for providing a signal radiation beam, and a bent structure for receiving the pump radiation beam and the signal radiation beam. The radiation propagation portion of the bent structure is made of a uniform Raman-active or uniform Kerr-nonlinear material and the radiation propagation portion comprises a dimension taking into account the spatial variation of the Raman susceptibility or Kerr susceptibility along the radiation propagation portion as experienced by radiation travelling along the bent structure for obtaining quasi-phase-matched four-wave-mixing in the radiation propagation portion. The dimension thereby is substantially inverse proportional with the linear phase mismatch for four-wave-mixing.

Abstract: 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.

Abstract: The present invention uses quantum interference of one and two photon absorption from a multiple color fields to optically inject ballistic spin currents in unbiased photoconductors. The spin currents can be generated with and without an accompanying electrical current and can be controlled using the relative phase of the colors. In one aspect of the there is provided a method of generating spin currents in a photoconductor material comprising producing a first coherent light beam having a first frequency &ohgr;1 and a second coherent light beam having a frequency twice the first frequency 2&ohgr;1, polarizing the first and second coherent light beams to have a preselected polarization with respect to each other, and simultaneously irradiating a selected region of the photoconductor material with the first coherent light beam and the second coherent light beam to generate a spin current in the photoconductor.

Abstract: 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.

Abstract: The present invention uses quantum interference of one and two photon absorption from a multiple color fields to optically inject ballistic spin currents in unbiased photoconductors. The spin currents can be generated with and without an accompanying electrical current and can be controlled using the relative phase of the colors. In one aspect of the there is provided a method of generating spin currents in a photoconductor material comprising producing a first coherent light beam having a first frequency &ohgr;1 and a second coherent light beam having a frequency twice the first frequency 2&ohgr;1, polarizing the first and second coherent light beams to have a preselected polarization with respect to each other, and simultaneously irradiating a selected region of the photoconductor material with the first coherent light beam and the second coherent light beam to generate a spin current in the photoconductor.

Abstract: 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.