Structures including a waveguide core and methods of fabricating a structure including a waveguide core. A back-end-of-line interconnect structure includes a cap layer, an interlayer dielectric layer, and one or more metal features embedded in the interlayer dielectric layer. The interlayer dielectric layer is stacked in a vertical direction with the cap layer. The one or more metal features have an overlapping arrangement in a lateral direction with the waveguide core, which is arranged under the back-end-of-line interconnect structure.

Various polarization rotator splitter (PRS) configurations are disclosed. In an example embodiment, a system includes a PRS that includes a silicon nitride (SiN) rib waveguide core that includes a rib and a ridge that extends vertically above the rib, the SiN rib waveguide core having a total height h.sub.SiN from a bottom of the rib to a top of the ridge, a rib height h.sub.rib from the bottom of the rib to a top of the rib, a rib width w.sub.rib, and a top width w.sub.SiN of the ridge. The rib width w.sub.rib varies along at least a portion of a length of the SiN rib waveguide core.

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.

An optical device including a core layer that includes an EO polymer, and clad layers that are disposed on and beneath the core layer, in which a polymer polymerized in a composition containing a reactive ionic liquid is used in the clad layers.

A flexible waveguide structure including a waveguide on a flexible substrate, both having transparent windows in the mid-infrared range, may serve as a photonic chemical sensor for measuring characteristic absorptions of analytes brought in physical contact with the waveguide. Such a sensor may, in accordance with some embodiments, be formed by an aluminum-nitride waveguide on a borosilicate substrate.

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.

An optical waveguide is disclosed. In a disclosed embodiment, the optical waveguide includes a first aluminum nitride (AlN) thin film disposed on a layer of high-frequency polymer. A second AlN thin film is embedded in the first AlN thin film. In disclosed embodiments, the nitrogen concentration level of the first AlN thin film is different than the concentration level of the second AlN thin film.

A system may include a polarization rotator combiner. The polarization rotator combiner may include a first stage, a second stage, and a third stage. The first stage may receive a first component of light with a TE00 polarization and a second component of light with the TE00 polarization. The first stage may draw optical paths of the first and second components together. The second stage may receive the first component and the second component from the first stage. The second stage may convert the polarization of the second component from the TE00 polarization to a TE01 polarization. The third stage may receive the first component and the second component from the second stage. The third stage may convert polarization of the second component from the TE01 polarization to a TM00 polarization. The third stage may output the first component and output the second component.

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.

A fabrication method produces a mechanically patterned layer of group III-nitride. The method includes providing a crystalline substrate and forming a first layer of a first group III-nitride on a planar surface of the substrate. The first layer has a single polarity and also has a pattern of holes or trenches that expose a portion of the substrate. The method includes then, epitaxially growing a second layer of a second group III-nitride over the first layer and the exposed portion of substrate. The first and second group III-nitrides have different alloy compositions. The method also includes subjecting the second layer to an aqueous solution of base to mechanically pattern the second layer.