Structures for a waveguide bend and methods of fabricating a structure for a waveguide bend. A waveguide bend is connected to a waveguide core. A slab layer, which is thinner than the waveguide bend, is coupled to the waveguide core and the waveguide bend. The slab layer includes a first curved opening and a second curved opening that is positioned between the first curved opening and a side surface of the waveguide bend. A section of the slab layer is positioned between the first and second curved openings. The first curved opening has a first radius, and the second curved opening has a second radius that is greater than or less than the first radius of the first curved opening.

Structures for a waveguide bend and methods of fabricating a structure for a waveguide bend. A waveguide bend is connected to a waveguide core. A slab layer, which is thinner than the waveguide bend, is coupled to the waveguide core and the waveguide bend. The slab layer includes a first curved opening and a second curved opening that is positioned between the first curved opening and a side surface of the waveguide bend. A section of the slab layer is positioned between the first and second curved openings. The first curved opening has a first radius, and the second curved opening has a second radius that is greater than or less than the first radius of the first curved opening.

Disclosed herein are configurations and methods to produce very low loss waveguide structures, which can be single-layer or multi-layer. These waveguide structures can be used as a sensing component of a small-footprint integrated optical gyroscope. By using pure fused silica substrates as both top and bottom cladding around a SiN waveguide core, the propagation loss can be well below 0.1 db/meter. Low-loss waveguide-based gyro coils may be patterned in the shape of a spiral (circular or rectangular or any other shape), that may be distributed among one or more of vertical planes to increase the length of the optical path while avoiding the increased loss caused by intersecting waveguides in the state-of-the-art designs. Low-loss adiabatic tapers may be used for a coil formed in a single layer where an output waveguide crosses the turns of the spiraling coil.

A photodiode which includes a core of a first waveguide that terminates in a tapered termination that extends above a core, made of germanium or of SiGe, of a second waveguide, a matching strip that extends opposite the tapered termination on one side and opposite the core of the second waveguide on the opposite side, this matching strip being coupled optically to the core of the second waveguide by an evanescent coupling and including a first zone inside which its effective propagation index is equal to the effective propagation index of a second zone of the tapered termination, these first and second zones optically coupling the tapered termination to the matching strip through a modal coupling, and a low-index layer that extends between the matching strip and the tapered termination.

An optical waveguide mounting substrate includes a wiring substrate, and an optical waveguide mounted on the wiring substrate with an adhesive layer being interposed therebetween. The optical waveguide includes a first cladding layer, a core layer formed on a surface of the first cladding layer facing toward the wiring substrate, and a second cladding layer formed on the surface of the first cladding layer facing toward the wiring substrate so as to cover a periphery of the core layer. An opening is opened on the second cladding layer-side, penetrating the second cladding layer and the core layer, and closed on the first cladding layer-side, and a metal film is provided on an end face of the core layer in the opening. The second cladding layer faces the wiring substrate via the adhesive layer. A part of the adhesive layer is filled in the opening.

Ceramic assembly can comprise a ceramic article comprising a thickness defined between a first major surface and a second major surface. The thickness can be about 100 micrometers or less. The ceramic assembly can comprise a polymer coating deposited over at least an outer peripheral portion of the first major surface of the ceramic article. The polymer coating can comprise a thickness of about 30 micrometers or less. An edge strength of the ceramic assembly can be greater than an edge strength of the ceramic article by about 50 MegaPascals or more. Methods of forming a ceramic assembly can comprise depositing a polymer coating on an outer peripheral portion of a first major surface of a ceramic article. Methods can further comprise curing the polymer coating.

A semiconductor structure includes a group III-V chiplet over a group IV substrate. A group IV optoelectronic device is situated in the group IV substrate. A patterned group III-V optoelectronic device is situated in the group III-V chiplet. A heating element is near the group IV optoelectronic device, or alternatively, near the patterned group III-V optoelectronic device. A dielectric layer is over the patterned group III-V optoelectronic device. A venting hole is in the dielectric layer in proximity of the heating element. A cavity is in the group IV substrate in proximity to the heating element.

An optical circuit capable of operating as a 90 optical hybrid includes a phase-symmetric optical splitter and a 90 optical splitter, and two 22 optical couplers as optical combiners. The input ports of the optical combiners and the output ports of the optical splitters face a common area therebetween, with the optical splitters interposed between optical combiners as viewed along the circumference of the common area. The output ports of each optical splitter is connected to closest input ports of the optical combiners with optical waveguides of a same length. The length of the waveguides may be minimized when the optical couplers and the optical splitters are disposed in a cross-like configuration.

Photonic devices having Al.sub.1-xSc.sub.xN and Al.sub.yGa.sub.1-yN materials, where Al is Aluminum, Sc is Scandium, Ga is Gallium, and N is Nitrogen and where 0<x0.45 and 0y1.

Disclosed herein are configurations and methods to produce very low loss waveguide structures, which can be single-layer or multi-layer. These waveguide structures can be used as a sensing component of a small-footprint integrated optical gyroscope. By using pure fused silica substrates as both top and bottom cladding around a SiN waveguide core, the propagation loss can be well below 0.1 db/meter. Low-loss waveguide-based gyro coils may be patterned in the shape of a spiral (circular or rectangular or any other shape), that may be distributed among one or more of vertical planes to increase the length of the optical path while avoiding the increased loss caused by intersecting waveguides in the state-of-the-art designs. Low-loss adiabatic tapers may be used for a coil formed in a single layer where an output waveguide crosses the turns of the spiraling coil.