Abstract: An integrated optical waveguide device, for example an optical phase modulator or an optical intensity modulator or a frequency converter, comprises a substrate (10) of a ferroelectric material having a first (11) and a second (12) surfaces perpendicular to a direction of spontaneous polarization of the ferroelectric material. At least the second surface is substantially inactive with respect to an operation of applying an externally generated electric field to the substrate. The device has at least one waveguide (18,19) integrated in the substrate in correspondence of the first surface thereof. At least a longitudinal waveguide section of the at least one waveguide is formed in a respective first substrate region (14,15;50) having a first orientation of spontaneous polarization. At least one second substrate region (15,14;51,52) is provided on the first surface adjacent to the first substrate region transversally to the longitudinal waveguide section.

Abstract: An integrated optical waveguide device comprises: a substrate (10) of a ferroelectric material; at least one waveguide (13;13A,13B) integrated in the substrate in correspondence of a surface (11) thereof; at least a longitudinal section (13;131,132,133;13A,13B) of the at least one waveguide is formed in a respective first substrate region (14;141,142,143;14A,14B;140A,140B;140C,140D) having a first orientation of spontaneous polarization. The first substrate region is sandwiched between at least two second substrate regions (15,16;151,161,152,162,153,163;15A,15B,17A,17B,16A,16B;150,1 60) which have a second orientation of spontaneous polarization, opposite to the first orientation, and are located at opposite sides of the waveguide section with respect to a longitudinal direction thereof.

Abstract: A coplanar integrated optical waveguide electro-optical modulator comprises a substrate (1) of an electro-optic material, at least two optical waveguides (41, 42) integrated in the substrate in correspondence of a surface (71) thereof, and an electrode system (80, 90, 100; 80, 90, 900; 12-15; 120, 130, 140, 150, 160, 170) arranged on the surface for applying a modulating electric field to the waveguides suitable for causing a modulation of a refractive index of the two waveguides in a device modulation region (50). The waveguides are formed, for at least a section thereof (411, 421) in the device modulation region, in respective substrate regions (61, 62) which have electro-optic coefficients of opposite sign along an axis transversal to the waveguide sections, so that a modulating electric field of same direction and orientation in the waveguide sections causes refractive index modulations of opposite sign in the waveguide sections.

Abstract: A method of and apparatus for creating a second order non-linearity profile along a waveguide. The method comprises: thermally poling a waveguide structure to generate a second order non-linearity; placing a mask adjacent to the waveguide structure; and exposing the waveguide structure with UV light through the mask to selectively erase the second order non-linearity along the waveguide structure. The mask may be an amplitude mask or phase mask. In a preferred embodiment an amplitude mask is used in combination with an incoherent UV light source to produce selective erasure of a thermally poled second order non-linearity. Apparatus for carrying out this method and devices based on waveguide structures fabricated using the method are also described.

Abstract: An optical parametric device for broadband parametric processes involving first and second frequencies &ohgr;1 and &ohgr;2. The device comprises an optical fiber comprising a core and a cladding, the cladding being microstructured with holes for providing waveguiding confinement of at least one optical mode in the core. The optical fiber is poled lengthwise with a non-linearity profile having a period that satisfies a quasi phase matching (QPM) condition including the first and second frequencies. Through the use of a poled holey fiber of suitable hole structure, it is possible to increase the second harmonic (SH) efficiency in comparison with poled conventional (non-holey) fiber. This is achieved by a combination of a low mode overlap area between the fundamental and SH waves, a low absolute value of the mode area, and a large SH bandwidth per unit length of the fiber, all of which can be provided together in a poled holey fiber.

Abstract: A method of creating a varying second order non-linearity profile along a waveguide, comprising: providing a waveguide structure with a waveguiding core and a surface adjacent to the waveguiding core; structuring the surface to produce a structured surface defining a varying distance between the structured surface and the waveguiding core along the waveguide; and thermally poling the waveguide structure to generate a varying second order non-linearity profile along the waveguide—derived from the varying distance between the structured surface and the waveguiding core. By the surface structuring the modulation of the second order non-linearly induced by the thermal poling can be enhanced. The waveguide structures can be used for making a variety of quasi-phase-matched (QPM) devices.

Abstract: A method of fabricating an optical fiber incorporating a volatile constituent, involving: (a) providing a preform comprising a cladding glass having an axial aperture and a core glass arranged in the axial aperture, wherein the working temperature of the core glass lies below the working temperature of the cladding glass; and (b) drawing the preform into an optical fiber at a drawing temperature that lies between the working temperatures of the core and cladding glasses and above the softening temperature of the cladding glass, wherein the core glass prior to drawing includes a dioxide or higher oxide compound of the volatile constituent having a Gibbs free energy of disassociation into a monoxide compound of the volatile constituent that is negative at the drawing temperature, whereby the dioxide or higher oxide compound tends to disassociate into the monoxide compound during drawing. The volatile constituent may be Sn or Pb. The method may also be adapted for incorporating P as the volatile constituent.