Abstract: An optical waveguide comprising an axial direction and a cross-section perpendicular to said axial direction is shown. The optical waveguide comprises a core region. The core region includes an integrally formed hologram, which extends along a first axial segment of the optical waveguide, the first axial segment having a first axial length. The hologram, seen in the cross-section, includes a micro-structure with written elements having a modified refractive index different from areas of the core region with an unmodified refractive index.

Abstract: An antenna capable of generating multiple beams that are close together and have side lobes of low level includes optics comprising a single main reflector and a set of primary sources, each source suitable for generating a beam taken up by the optics that transmits it, or suitable for receiving a beam picked up by the optics of the antenna. The main reflector has an aperture of diameter D as a function of the center wavelength of the frequency band of the beams and the half-power beam width of the beams coming from the main antenna element, and a dimensionless number lying in the range 1.5 to 4. The optics present a profile that is modified relative to conventional optics comprising a parabolic main reflector by a correction that imparts an amplitude and phase distribution that is preferably circularly symmetrical, and compliant with a relationship for enlarging the reflected beams.

Abstract: An antenna capable of generating multiple beams that are close together and have side lobes of low level includes optics comprising a single main reflector and a set of primary sources, each source suitable for generating a beam taken up by the optics that transmits it, or suitable for receiving a beam picked up by the optics of the antenna. The main reflector has an aperture of diameter D as a function of the center wavelength of the frequency band of the beams and the half-power beam width of the beams coming from the main antenna element, and a dimensionless number lying in the range 1.5 to 4. The optics present a profile that is modified relative to conventional optics comprising a parabolic main reflector by a correction that imparts an amplitude and phase distribution that is preferably circularly symmetrical, and compliant with a relationship for enlarging the reflected beams.

Abstract: The invention provides a method for measuring in situ the amount of material removed by laser ablation with ultrashort laser pulses. The method relies on the geometrical information provided by the backscattered light from the ablating laser. The temporal structure of the backscattered laser light is used to provide an accurate measure for the depth of the ablated area, since the round-trip time for the short laser pulses uniquely determines the distance to the object under illumination. For femtosecond laser pulses a depth resolution of a few micrometers can be achieved. According to the invention, imaging of the backscattered light from a single ablating pulse provides all the information necessary to derive a cross-sectional profile across the ablated region.

Abstract: A large scan antenna, particularly for embarked use on board a satellite and for operation in the ultrahigh frequency range, of the type formed of a feed and a main fixed secondary reflector, the antenna being readily foldable into a launching configuration with a minimum of component elements, and comprising at least one guide G each formed of a first and a second parabolic secondary reflectors (12, 13) aligned optically along the axis of the wave guide G between the feed (10) and the main reflector (15), said wave guide G being on the one hand variable in length by moving at least one (13) of said secondary reflectors with respect to the other (12) along the axis (14) of the wave guide G, and on the other hand, rotatable about the axis (11) of the feed (10).