In one aspect the invention provides a graded refractive index single crystal waveguide having a glass block containing at least one crystal core, the crystal core having a central portion extending along an axis from a first end to a second end; an interface defining a peripheral boundary of the crystal core at a junction of the crystal core and an adjacent portion of the glass block, and a continuous, radially symmetric misorientation transverse to the central portion; wherein the misorientation has a misorientation angle that increases with increasing distance from the central portion towards the interface.

In one aspect the invention provides a graded refractive index single crystal waveguide having a glass block containing at least one crystal core, the crystal core having a central portion extending along an axis from a first end to a second end; an interface defining a peripheral boundary of the crystal core at a junction of the crystal core and an adjacent portion of the glass block, and a continuous, radially symmetric misorientation transverse to the central portion; wherein the misorientation has a misorientation angle that increases with increasing distance from the central portion towards the interface.

A manufacturing system for fabricating optical waveguides includes a diffusion channel with a plurality of inlets at a first end and an outlet at a second end opposite to the first end and separated from the inlets by a channel length. Each of the plurality of inlets includes a central inlet flowing a first resin into the diffusion channel such that the first resin flows along the channel length of the diffusion channel toward the outlet, and an outer inlet flowing a second resin along a periphery of the first resin. The second resin may have an index of refraction different than the first resin. The diffusion may occur between portions of the first resin and portions of the second resin over the channel length to form a composite resin having a profile with a plurality of indices of refraction in at least one dimension.

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.

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.

A waveguide having a gradient-index (GRIN) waveguide lateral coupler is provided. In an example embodiment, the waveguide comprises an active region. The refractive index profile of the active region is non-constant.

A refractive index device and method of making it include obtaining a glass structure comprising a plurality of nucleation sites. The glass structure is formed from a glass composition that comprises a first chemical component and a second chemical component. A crystal of the second chemical component has a different second refractive index from a first refractive index of the first chemical component. Each nucleation site defines where a crystal of the second chemical component can be grown. The method includes causing crystals of the second chemical component to grow in situ at a set of the plurality of nucleation sites in order to produce a spatial gradient of a refractive index in the glass structure.

The variable optical splitter system includes a V-shaped optical splitter for use in planar lightwave circuits (PLCs), photonic integrated circuits (PICs), etc. The V-shaped optical splitter has first and second optically transmissive branches sharing a common optically transmissive base, where the first and second optically transmissive branches each define an optical waveguide. The first and second optically transmissive branches are symmetrically angled about a central longitudinal axis. A light source directs a light beam to a laterally extending input surface of the optically transmissive base. The light beam travels parallel to the central longitudinal axis. The optical power splitting ratio is directly proportional to the input beam's displacement from the central longitudinal axis, permitting selective tuning of the ratio during design of the splitter.

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.

In one aspect the invention provides a graded refractive index single crystal waveguide having a glass block containing at least one crystal core, the crystal core having a central portion extending along an axis from a first end to a second end; an interface defining a peripheral boundary of the crystal core at a junction of the crystal core and an adjacent portion of the glass block, and a continuous, radially symmetric misorientation transverse to the central portion; wherein the misorientation has a misorientation angle that increases with increasing distance from the central portion towards the interface.