An embodiment is an optical connection element including a first waveguide core and a second waveguide core on a substrate, the first waveguide core and the second waveguide core configured to propagate a signal light and a resin-curing light, and a mode field conversion portion provided at one end of the first waveguide core, wherein the second waveguide core covers at least the mode field conversion portion on the substrate, and a refractive index of the first waveguide core is higher than a refractive index of the second waveguide core.

Phase-change metasurface waveguide mode converters and photonic computing systems including a phase-change metasurface waveguide mode converter are described. In an embodiment, the phase-change metasurface waveguide mode converter include a plurality of phase-change antennae comprising a phase-change material and protruding from a surface, wherein each phase-change antenna of the plurality of phase-change antennae is configured to scatter an optical waveguide mode and cause a phase shift of light travelling through an optical waveguide optically coupled thereto. In an embodiment, the phase-change metasurface waveguide mode converter includes the plurality of phase-change antennae configured to alternate between a crystalline phase and an amorphous phase.

A waveguide including a multimode optical fiber joined to a structure for concentrating the guided modes spatially. The concentrating structure exhibits an adiabatic variation in its transverse dimension d.sub.pc in the direction of its exit face, and its transverse dimension d.sub.pc has a value d.sub.pc,in at least equal to a value d.sub.fc of the transverse dimension d.sub.fc of the core of the multimode optical fiber at the second face thereof.

A fiber optic test device is provided that includes a light source pigtailed with a first end of a non-bend insensitive multimode fiber (non-BIMMF). A second end of the non-BIMMF is fusion spliced to a first end of a reference grade bend insensitive multimode fiber (BIMMF). A reference grade optical fiber connector is attached to a second end of the BIMMF, which is coupled to a first end of a reference grade bulkhead adapter. The non-BIMMF is deformed so that a specific launch condition, such as encircled flux, is achieved at the first end of the BIMMF. A test reference cord, which contains a reference grade BIMMF having similar geometric properties as the BIMMF that is fusion spliced to the non-BIMMF, is attached to a second end of the bulkhead adapter. Modal transparency is achieved and the launch condition is maintained at the output of the test reference cord.

Optical waveguide cores having refractive index profiles that vary angularly about a propagation axis of the core can provide single-mode operation with larger core diameters than conventional waveguides. In one representative embodiment, an optical waveguide comprises a core that extends along a propagation axis and has a refractive index profile that varies angularly about the propagation axis. The optical waveguide can also comprise a cladding disposed about the core and extending along the propagation axis. The refractive index profile of the core can vary angularly along a length of the propagation axis.

In the examples provided herein, an apparatus has a mode converter coupled to a first waveguide to convert light propagating in a first set of spatial modes along the first waveguide to a second set of spatial modes. The apparatus also has a second waveguide coupled to the mode converter, where the second set of spatial modes propagate along the second waveguide in a first direction away from the mode converter. Further, the apparatus includes a coupler to couple a portion of the light propagating in the second set of spatial modes out of the second waveguide. Additionally, the second waveguide has an end facet away from the mode converter to reduce back reflection of the light not coupled out of the second waveguide to the first waveguide.

In the examples provided herein, an apparatus has a mode converter coupled to a first waveguide to convert light propagating in a first set of spatial modes along the first waveguide to a second set of spatial modes. The apparatus also has a second waveguide coupled to the mode converter, where the second set of spatial modes propagate along the second waveguide in a first direction away from the mode converter. Further, the apparatus includes a coupler to couple a portion of the light propagating in the second set of spatial modes out of the second waveguide. Additionally, the second waveguide has an end facet away from the mode converter to reduce back reflection of the light not coupled out of the second waveguide to the first waveguide.

An optical mode converter includes a silicon substrate and a silicon dioxide film deposited on a top surface of the silicon substrate. A lithium niobate waveguide positioned on the silicon dioxide film having a slab and a rib that both taper in a direction of beam propagation through the optical mode converter. A doped silicon dioxide waveguide is positioned on top of the lithium niobate waveguide and has a slab that tapers in the direction of the optical beam propagation through the optical mode converter. The optical mode converter expands an optical mode of the optical beam propagating through the optical mode converter from a first optical mode size to a second optical mode size.

An optical mode converter includes a silicon substrate and a silicon dioxide film deposited on a top surface of the silicon substrate. A lithium niobate waveguide positioned on the silicon dioxide film having a slab and a rib that both taper in a direction of beam propagation through the optical mode converter. A doped silicon dioxide waveguide is positioned on top of the lithium niobate waveguide and has a slab that tapers in the direction of the optical beam propagation through the optical mode converter. The optical mode converter expands an optical mode of the optical beam propagating through the optical mode converter from a first optical mode size to a second optical mode size.

A method and mode conversion waveguide system for converting a mode of a light is provided. The light is sent through a single mode waveguide, wherein the light has a first mode while traveling through single mode waveguide. The light is sent from the single mode waveguide into a multimode interference region having connected to the single mode waveguide. The light is reflected with a cavity within the multimode interference region in a manner that causes the light to propagate away from the single mode waveguide. The light is output from multimode interference region, wherein the light has a second mode.