Embodiments of the disclosure provide an optical polarizer with a varying vertical thickness, and methods to form the same. An optical polarizer according to the disclosure may include a first waveguide core over a semiconductor substrate. A first cladding material is on at least an upper surface of the first waveguide core. A second waveguide core over the first waveguide core and above the first cladding material. The second waveguide core includes a first segment having a vertical thickness that varies along a length of the first segment. A second cladding material is at least partially surrounding the second waveguide core. Transfer of one of a transverse electric (TE) mode signal and a transverse magnetic (TM) mode signal from the first waveguide core to the second waveguide core occurs between the first segment of the second waveguide core and the first waveguide core.

An optical assembly for realizing horizontal and vertical spot-size conversion to couple light from a thin waveguide to a thick waveguide is disclosed. The assembly comprises at least one first thin waveguide with a first section having a first optical mode field and a horizontal spot-size expansion section providing spot-size conversion for a first horizontal dimension of said first optical mode field of a light beam propagating in said first waveguide, and at least one second thick waveguide with a second section having a second optical mode field and a horizontal spot-size reduction section providing spot-size conversion for a second horizontal dimension of said second optical mode field of a light beam propagating in said second waveguide. The expanded end of said first waveguide is aligned and rotated to interface with the reduced end of said second waveguide, so that the mode fields in said first and second waveguides are rotated 90 degrees with respect to each other, whereby the spot size of a light beam so coupled between the first and second waveguides is expanded or shrunk in both transverse dimensions, depending on the direction of the light beam.

Disclosed are embodiments of a photonic integrated circuit (PIC) structure with a waveguide core having tapered sidewall liner(s) (e.g., symmetric tapered sidewall liners on opposing sides of a waveguide core, asymmetric tapered sidewall liners on opposing sides of a waveguide core, or a tapered sidewall liner on one side of a waveguide core). In some embodiments, the tapered sidewall liner(s) and waveguide core have different refractive indices. In an exemplary embodiment, the waveguide core is a first material (e.g., silicon) and the tapered sidewall liner(s) is/are a second material (e.g., silicon nitride) with a smaller refractive index than the first material. In another exemplary embodiment, the waveguide core is a first compound and the tapered sidewall liner(s) is/are a second compound with the same elements (e.g., silicon and nitrogen) as the first compound but with a smaller refractive index. Also disclosed are method embodiments for forming such a PIC structure.

In a waveguide having a given Δ, a low-loss waveguide bend is realized while the curvature radius is kept small. In an optical waveguide in which a first waveguide and a second waveguide are connected, a clothoid tapered waveguide bend is inserted between the first waveguide and the second waveguide. In the clothoid tapered waveguide bend, the waveguide width continuously changes from a first waveguide width at a connection point of the first waveguide to a second waveguide width at a connection point of the second waveguide, the curvature radius continuously changes from a first curvature radius at the connection point of the first waveguide to a second curvature radius at the connection point of the second waveguide, the first waveguide width and the second waveguide width are different from each other, and the first curvature radius and the second curvature radius are different from each other.

Structures for a photodetector or terminator and methods of fabricating a structure for a photodetector or terminator. The structure includes a waveguide core having a longitudinal axis, a pad connected to the waveguide core, and a light-absorbing layer on the pad adjacent to the waveguide core. The light-absorbing layer includes an annular portion, a first taper, and a second taper laterally spaced from the first taper. The first taper and the second taper are positioned adjacent to the waveguide core.

The present disclosure generally relates to structures for use in optoelectronic/photonic applications and integrated circuit (IC) chips. The present disclosure also relates to semiconductor devices having a photodetector coupled with a waveguide, more particularly, a photodetector with a butt-end coupled waveguide. The present disclosure provides a structure having a substrate, a photodetector arranged above the substrate, the photodetector having a core body and a coupler that is adjacent to the core body, in which the core body is configured to absorb light received by the coupler, and the coupler including a plurality of grating structures having respective widths that vary as a function of position relative to the core body.

A photonic Y-splitter includes a substrate, first optical waveguides disposed in the substrate on a first layer, the first optical waveguides may be flared at a first end and inverse tapered toward a second end and may be substantially mirror images of one another, and a second optical waveguide disposed in the substrate on a second layer, above the first layer, the second optical waveguide being centered over the first optical waveguides and longitudinally arranged between the first end and the second end.

An optical semiconductor element includes an optical receiver including a first semiconductor layer, a heater for heating the first semiconductor layer; and a monitor. A first semiconductor layer that absorbs light and generates electric carriers; a heater for heating the first semiconductor layer; and a monitor including a second semiconductor layer in which dark current is changed by heat generated by the heater.

An optical connection element includes a first waveguide core and a second waveguide core above a substrate or a cladding and in which signal light and resin curing light propagate through the first waveguide core and the second waveguide core, the optical connection element including: an inter-core light coupling section in which a part of the first waveguide core and a part of the second waveguide core overlap in a perpendicular direction; and a resin curing light coupling section that couples resin curing light to the second waveguide core.

A multi-chip photonic assembly includes first and second photonic integrated circuits having first and second waveguides vertically stacked such that first vertical dimensions of the first and second waveguides occupy different horizontal planes in the stack. At least one of the first and second waveguides has a region that has a second vertical dimension that is larger than the first vertical dimension and either horizontally overlaps the other waveguide and/or vertically contacts the other waveguide. Light moving through one of the waveguides from the first vertical dimension to the other vertical dimension changes modes vertically so that the light moves from one waveguide to the other.