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.

Optical apparatus and methods of manufacture thereof An optical apparatus (20) for evanescently coupling an optical signal across an (interface (30) is described. The optical apparatus (20) comprises a first substrate (22) and a second substrate (24). The optical signal is evanescently coupled between a first waveguide (26) formed by laser inscription of the first substrate (22) and a second waveguide (28) of the second substrate (22). The first waveguide (26) comprises a curved section (34) configured to provide evanescent coupling of the optical signal between the first and second waveguides (26, 28) via the interface (30).

An optical waveguide provided and includes: a core forming layer with a high refractive index; and a first clad layer with a low refractive index, bonded to a first main surface of the core forming layer. The core forming layer is provided in its plane direction with a core portion, lateral clad portions each having one side adjacent to a corresponding side of the core portion, and high refractive index portions each adjacent to the other side of a corresponding one of the lateral clad portions. The core portion is provided in its plane direction with a central region, and GI regions in each of which a refractive index continuously decreases from the central region toward an interface with the corresponding one of the lateral clad portions. The lateral clad portions each include a region having a constant refractive index.

An optical apparatus 20 for evanescently coupling an optical signal across an interface 30 is described. The optical apparatus 20 comprises a first substrate 22 and a second substrate 24. The optical signal is evanescently coupled between a first waveguide 26 formed by laser inscription of the first substrate 22 and a second waveguide 28 of the second substrate 22. The first waveguide 26 comprises a curved section 34 configured to provide evanescent coupling of the optical signal between the first and second waveguides 26, 28 via the interface 30.

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 production method for an optical waveguide including: a first step of inserting a needle-like portion at a tip end of an ejection unit into uncured cladding; a second step of moving the needle-like portion in the uncured cladding while ejecting an uncured material from the needle-like portion to form an uncured core surrounded and covered with the uncured cladding; a third step of removing the needle-like portion from the uncured cladding; and a fourth step of curing the uncured cladding and core, wherein the uncured cladding is composed of a composition including a reactive silicone compound composed of a polycondensate of a diarylsilicic acid compound of Formula [1]

##STR00001##

and an alkoxy silicon compound of Formula [2]

Ar.sup.3Si(OR.sup.1).sub.aR.sup.2.sub.3-a[2],

and a di(meth)acrylate compound of Formula [3]

##STR00002##

and the uncured core is composed of a composition including a reactive silicone compound and an aromatic vinyl compound of Formula [4]

##STR00003##

A production method for an optical waveguide including: a first step of inserting a needle-like portion at a tip end of an ejection unit into uncured cladding; a second step of moving the needle-like portion in the uncured cladding while ejecting an uncured material from the needle-like portion to form an uncured core surrounded and covered with the uncured cladding; a third step of removing the needle-like portion from the uncured cladding; and a fourth step of curing the uncured cladding and core, wherein the uncured cladding is composed of a composition including a reactive silicone compound composed of a polycondensate of a diarylsilicic acid compound of Formula [1] ##STR00001##
and an alkoxy silicon compound of Formula [2]
Ar.sup.3Si(OR.sup.1).sub.aR.sup.2.sub.3-a[2]
and a di(meth)acrylate compound of Formula [3] ##STR00002##
and the uncured core is composed of a composition including a reactive silicone compound and an aromatic vinyl compound of Formula [4] ##STR00003##

An optical apparatus 20 for evanescently coupling an optical signal across an interface 30 is described. The optical apparatus 20 comprises a first substrate 22 and a second substrate 24. The optical signal is evanescently coupled between a first waveguide 26 formed by laser inscription of the first substrate 22 and a second waveguide 28 of the second substrate 22. The first waveguide 26 comprises a curved section 34 configured to provide evanescent coupling of the optical signal between the first and second waveguides 26, 28 via the interface 30.

An optical polarization converter includes an optical waveguide. A portion of the optical waveguide has an asymmetric cross-section profile. For example, a cross-section of the portion of the optical waveguide may not have symmetry associated with a horizontal axis and may not have symmetry associated with a vertical axis. The portion of the optical waveguide is tapered. For example, the portion of the optical waveguide may be associated with one or more taper ratios. The portion of the optical waveguide is configured to convert a polarization mode of an optical beam from a first fundamental polarization mode to a second fundamental polarization mode, such as from a fundamental transverse electric (TE) polarization mode to a fundamental transverse magnetic (TM) polarization mode (or vice versa).

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.