The present disclosure relates to semiconductor structures and, more particularly, to waveguide attenuators and methods of manufacture. The structure includes: a main bus waveguide structure; a first hybrid waveguide structure evanescently coupled to the main bus waveguide structure and comprising a first geometry of material; and a second hybrid waveguide structure evanescently coupled to the main bus waveguide structure and comprising a second geometry of the material.

A multi-level semiconductor device, the device including: a first level including integrated circuits; a second level including a structure designed to conduct electromagnetic waves, where the second level is disposed above the first level, where the integrated circuits include single crystal transistors; and an oxide layer disposed between the first level and the second level, where the integrated circuits include at least one processor, where the second level is bonded to the oxide layer, and where the bonded includes oxide to oxide bonds.

Disclosed is a photonic structure and associated method. The structure includes a closed-curve waveguide having a first height, as measured from the top surface of an insulator layer, and an outer curved sidewall that extends essentially vertically the full first height (e.g., to minimize signal loss). The structure includes a closed-curve thermal coupler and a heating element. The closed-curve thermal coupler is thermally coupled to and laterally surrounded by the closed-curve waveguide and has a second height that is less than the first height. In some embodiments, the closed-curve waveguide and the closed-curve thermal coupler are continuous portions of the same semiconductor layer having different thicknesses. The heating element is thermally coupled to the closed-curve thermal coupler and thereby indirectly thermally coupled to the closed-curve waveguide. Thus, the heating element is usable for thermally tuning the closed-curve waveguide via the closed-curve thermal coupler to minimize any temperature-dependent resonance shift (TDRS).

A light detection and ranging system can employ a metal insulator metal tunnel junction positioned atop a substrate. Activation of the metal insulator metal tunnel junction by a signal from a controller can generate light via inelastic scattering. Light to be used to detect downrange targets can be combined from multiple junctions via a multimode interference combiner.

An optical fiber array includes a V-groove substrate in which a V-groove for optical fiber alignment is formed, a pressing plate laminated and bonded on the V-groove substrate, and an optical fiber bonded and fixed in the V-groove of the V-groove substrate, wherein a distance between the optical fiber and the V-groove is less than 20 μm.

Techniques and mechanisms for optically coupling a photonic integrated circuit (PIC) chip to an optical fiber via a planar optical waveguide structure. In an embodiment, a PIC chip comprises integrated circuitry, photonic waveguides, and integrated edge-oriented couplers (IECs) which are coupled to the integrated circuitry via the photonic waveguides. The PIC chip forms respective divergent lens surfaces of the IECs, which are each at a respective terminus of a corresponding one of the photonic waveguides. A planar optical waveguide structure, which is adjacent to the IECs, comprises a core which is optically coupled between the PIC chip and an array of optical fibers. In another embodiment, an edge of the PIC forms a stepped structure, wherein an upper portion of the stepped structure comprises the plurality of coplanar IECs, and a lower portion of the stepped structure extends past the plurality of coplanar IECs.

Structures for an optical power splitter and methods of forming a structure for an optical power splitter. The structure includes a first waveguide core having a first arm, a second waveguide core including a second arm, and a third waveguide core having a third arm laterally positioned between the first arm and the second arm. The third arm has a longitudinal axis. The first arm is longitudinally offset from the third arm parallel to the longitudinal axis such that the third arm and the first arm are laterally adjacent over a first overlap distance. The second arm is longitudinally offset from the third arm parallel to the longitudinal axis such that the third arm and the second arm are laterally adjacent over a second overlap distance. The first overlap distance is greater than the second overlap distance to provide an overlap offset.

Silicon photonic integrated circuit (PIC) on a multi-zone semiconductor on insulator (SOI) substrate having at least a first zone and a second zone. Various optical devices of the PIC may be located above certain substrate zones that are most suitable. A first length of a photonic waveguide structure comprises the crystalline silicon and is within the first zone, while a second length of the waveguide structure is within the second zone. Within a first zone, the crystalline silicon layer is spaced apart from an underlying substrate material by a first thickness of dielectric material. Within the second zone, the crystalline silicon layer is spaced apart from the underlying substrate material by a second thickness of the dielectric material.

A photodetector structure over a partial length of a silicon waveguide structure within a photonic integrated circuit (PIC) chip. The photodetector structure is embedded within a cladding material surrounding the waveguide structure. The photodetector structure includes an absorption region, for example comprising Ge. A sidewall of the cladding material may be lined with a sacrificial spacer. After forming the absorption region, the sacrificial spacer may be removed and passivation material formed over a sidewall of the absorption region. Between the absorption region an impurity-doped portion of the waveguide structure there may be a carrier multiplication region, for example comprising crystalline silicon. If present, edge facets of the carrier multiplication region may be protected by a spacer material during the formation of an impurity-doped charge carrier layer. Occurrence of edge facets may be mitigated by embedding a portion of the photodetector structure with a thickness of the waveguide structure.

The present invention provides an optical coupler comprising: a first optical prong; a second optical prong; an optical waveguide with which the first optical prong and the second optical prong merge; wherein: a distance from an axially outer tip edge of the first optical prong to an axially outer tip edge of the first optical prong is greater than a planar width of the optical waveguide; and the first optical prong and the second optical prong are each tapered from the optical waveguide.