Abstract: Structures including a waveguide core and methods of fabricating a structure including a waveguide core. A back-end-of-line interconnect structure has an interlayer dielectric layer and a cap layer stacked over the interlayer dielectric layer. A waveguide core includes a section arranged beneath the cap layer. The waveguide core has a first index of refraction that varies as a function of width, and the cap layer has a second index of refraction. The section of the waveguide core has a width that is selected such that the first index of refraction is substantially equal to the second index of refraction to provide phase matching effective for coupling a portion of an optical signal from the waveguide core to the cap layer.

Abstract: Structures with waveguides in multiple levels and methods of fabricating a structure that includes waveguides in multiple levels. A waveguide crossing has a first waveguide and a second waveguide arranged to intersect the first waveguide. A third waveguide is displaced vertically from the waveguide crossing, The third waveguide includes a portion having an overlapping arrangement with a portion of the first waveguide. The overlapping portions of the first and third waveguides are configured to transfer optical signals between the first waveguide and the third waveguide.

Abstract: Structures that include an optical component, such as a grating coupler, and methods of fabricating a structure that includes an optical component, such as a grating coupler. First and second layers are arranged over the optical component with the first layer arranged between the second layer and the optical component. The first and second layers are each composed of a tunable material having a refractive index that is a function of a bias voltage applied to the first layer and the second layer.

Abstract: Structures that include a waveguide and methods of fabricating a structure that includes a waveguide. A tapered feature composed of a dielectric material is arranged over the waveguide. The tapered feature includes a sidewall that is angled relative to a longitudinal axis of the waveguide.

Abstract: Structures for a polarization splitter and methods of forming a polarization splitter. A multi-mode interference region includes a first waveguide and a second waveguide arranged in a stack over the first waveguide. First and second input ports are connected with the multi-mode interference region. First and second output ports are connected with the multi-mode interference region.