Abstract: A doped slab region is described for use around a ridge waveguide, for controlling the refractive index of the waveguide material. Instead of simply diffusing dopant in from a surface of the slab region adjacent the waveguide, an area of the slab region is etched and dopant diffused in from a side face of the etched region. Thus, the dopant profile is established from a horizontal direction, allowing the profile to be controlled. A simple vertically uniform doping profile can thus be provided, leading to a vertically uniform current density, or an anisotropic wet etch can be applied after the initial etch to provide a profile which concentrates the current density at a selected height in the slab region.

Abstract: The device comprises an upper silicon layer (10) including two optically connected rib waveguides (3,4) formed in the upper silicon layer (10); a pair of dissimilar materials (6,7) each positioned between the two waveguides (3,4); and an electrical circuit (8,9,13) through the pair of dissimilar materials (6,7), so that an electrical current can be passed through the dissimilar materials (6,7) in both forward and reverse directions, so as to simultaneously heat one waveguide and cool the other waveguide by virtue of the Peltier effect.

Abstract: An apparatus is provided for coupling an optical fibre to a waveguide on an optical chip, the apparatus comprises a recess in the chip for receiving the optical fiber, the recess comprising a V-groove the side faces of which locate the position of the fiber in directions perpendicular to the optical axis of the fiber so as to position the fibre in alignment with the waveguide, and an end face adjacent the end of the waveguide, the end face of the recess being substantially flat and substantially perpendicular to the plane of the chip with its normal inclined to the optical axis of the waveguide so an optical fiber having an inclined end face can be brought into a close, abutting relationship with the end of the waveguide and brought into rotational alignment therewith about its optical axis by positioning the fiber so its inclined end face lies in planar contact with the end face of the recess.