The present invention relates to a composite optical waveguide (1) containing a polymer optical waveguide and a silicon optical waveguide adiabatically coupled to each other, in which the polymer optical waveguide and the silicon optical waveguide are coupled to each other by an adhesive layer in an adiabatic-coupling portion where a core of the polymer optical waveguide and a core of the silicon optical waveguide are disposed to face each other, the adhesive layer is formed by using a photocurable adhesive having a glass transition point Tg being 125 C. or higher after curing, and the adiabatic-coupling portion includes a region in which a spacing t between the core of the polymer optical waveguide and the silicon optical waveguide is 1.5 m or less.

The invention relates to an optical coupling device for coupling a first waveguide, for example a multi-mode waveguide, to a second waveguide, for example a single-mode waveguide. The device is formed in a core layer and comprises a focusing structure (SF) capable of converting a light beam from a target mode of the first waveguide to a target mode of the second waveguide. The focusing structure comprises a plurality of trenches (T1-T4) made in the core layer to create a pseudo graded refractive index, itself able to convert the light beam from the target mode of the first waveguide to the target mode of the second waveguide.

The scope of the invention extends to a photonic circuit comprising a single-mode waveguide, a multi-mode waveguide and a device according to the invention for coupling the single-mode waveguide to the multi-mode waveguide. The multi-mode waveguide can comprise a surface coupling network in order to allow for coupling with an optical fibre.

Optical component and methods for forming optical components are described. The optical component includes a substrate having a base and a fin extending from the base, a buffer layer formed on the substrate leaving a portion of the fin exposed, and a confinement layer deposited over the buffer layer and the fin. The refractive index of the substrate is greater than the refractive index of the confinement layer, and the refractive index of the confinement layer is greater than the refractive index of the buffer layer.

A resin optical waveguide containing a core, an under cladding and an over cladding having refractive indices lower than that of the core, in which the resin optical waveguide has, at one end side of, a core-exposed section at which the over cladding is not present and the core and the under cladding nearby the core are exposed and, of the under cladding, a portion corresponding to the core-exposed section has a first layer and a second layer that satisfy a certain condition.

A resin optical waveguide containing a core, an under cladding and an over cladding having refractive indices lower than that of the core, in which the resin optical waveguide has, at one end side thereof, a core-exposed section at which the over cladding is not present and the core is exposed and, of the under cladding, a portion corresponding to the core-exposed section has a core-neighboring region that satisfies the following (1) and (2): (1) the core-neighboring region is a region whose distance from the core is within x, and x is 5 m or more and 20 m or less; and (2) the core-neighboring region has a refractive index distribution that the refractive index at a side of an interface with the core is high and the refractive index at a far side from the interface with the core is low.