Abstract: A method of generating light is disclosed. The method comprises irradiating a substance with first optical field of a first frequency and second optical field of a second frequency. The second frequency being higher than a cutoff frequency of a harmonics generation spectrum characterizing the interaction of the substance with the first optical field.

Abstract: A device (10) for producing high frequency radiation using a source of elliptically polarized radiation is disclosed based on: irradiating a frequency multiplication medium having a screw axis (16) symmetry of approximate Nth order symmetry, oriented so that said elliptically polarized radiation propagates in parallel to the screw axis (16). Also, a method for producing high frequency radiation is disclosed based on irradiating a frequency multiplication medium having a screw axis (16) of approximate Nth order symmetry with elliptically polarized radiation so that the elliptically polarized radiation propagates in parallel to the screw axis (16). Furthermore, a method of producing a beam of high frequency radiation composed of only a limited number of wavelengths is disclosed whereby the intensity of a beam (22) interacting with a frequency multiplication medium is selected so that only a limited number of wavelengths is emitted.

Abstract: A device (10) for producing high frequency radiation using a source of elliptically polarized radiation is disclosed based on: irradiating a frequency multiplication medium having a screw axis (16) symmetry of approximate Nth order symmetry, oriented so that said elliptically polarized radiation propagates in parallel to the screw axis (16). Also, a method for producing high frequency radiation is disclosed based on irradiating a frequency multiplication medium having a screw axis (16) of approximate Nth order symmetry with elliptically polarized radiation so that the elliptically polarized radiation propagates in parallel to the screw axis (16). Furthermore, a method of producing a beam of high frequency radiation composed of only a limited number of wavelengths is disclosed whereby the intensity of a beam (22) interacting with a frequency multiplication medium is selected so that only a limited number of wavelengths is emitted.

Abstract: The invention is a waveguide structure (10) that includes two waveguides (90, 94) flanking a coupling region (92) whose effective refractive index is less than those of the waveguides. Outboard of the waveguides are bounding regions (88, 96) whose effective refractive indices decrease inwards adiabatically at the proximal and distal ends of the bounding regions. The waveguides are coupled optically by periodic perturbations of the waveguide geometry, or by reversible uniform or periodic perturbations of the effective refractive indices. In an optical switch matrix based on the waveguide structure, all the waveguides are straight and parallel. A second aspect of the invention is a directional coupler comprising mechanisms for reversibly and quasiperiodically perturbing the effective refractive indices of the waveguides. The respective envelope functions vary monotonically in opposite senses.

Abstract: A source of intense coherent high-frequency electromagnetic radiation such as soft x-rays. A circularly polarized incident beam of coherent radiation is directed at a frequency multiplication medium that includes constituents of approximate Cn symmetry, oriented so that the symmetry axes of the constituents are parallel to the incident beam. The interaction of the incident beam and the constituents of the medium produces higher harmonics of the incident frequency, up into the x-ray band. If the Cn symmetry of the medium constituents is exact then the harmonic frequencies are multiples ln±l of the frequency of the incident beam, where l is an integer. If the Cn symmetry is only approximate, then the harmonics are centered around these multiples. Suitable medium constituents include dipolar molecules of C5v symmetry and circular rings of nanoparticles.

Abstract: An optical coupler, for coupling two waveguides, and an optical switch based on the optical coupler. The indices of refraction of parallel sections of the two waveguides are reversibly perturbed periodically in space to couple low order modes in the two waveguides via a high order mode common to the two waveguides. The waveguides are thus couples with a beat length that may be five or more orders of magnitude shorter than it would be without the periodic perturbations.