A mode field adapter (MFA) is disclosed. The MFA is tapered and includes a passive core region and an active core region separated by a distance. Further, the passive core region includes first and second passive layers that are separated by another distance. The MFA is configured to receive an optical signal from a first waveguide, and alter, for transmission to a second waveguide, an optical mode of the optical signal. The optical mode is altered based on the distance between the first and second passive layers, the distance between the active and passive core regions, and the tapering of the MFA. The optical mode is altered such that an optical loss associated with the optical signal traversing from the first waveguide to the second waveguide by way of the MFA is within a tolerance limit.

The invention described herein pertains to the structure and formation of dual core waveguide structures and to the formation of optical devices including spot size converters from these dual core waveguide structure for the receiving and routing of optical signals on substrates, interposers, and sub-mount assemblies.

An optical mode converter includes a silicon substrate and a silicon dioxide film deposited on a top surface of the silicon substrate. A lithium niobate waveguide positioned on the silicon dioxide film having a slab and a rib that both taper in a direction of beam propagation through the optical mode converter. A doped silicon dioxide waveguide is positioned on top of the lithium niobate waveguide and has a slab that tapers in the direction of the optical beam propagation through the optical mode converter. The optical mode converter expands an optical mode of the optical beam propagating through the optical mode converter from a first optical mode size to a second optical mode size.

An easy-to-fabricate and highly efficient single-mode optical fiber-to-single-mode optical waveguide coupler having relatively large horizontal and vertical alignment tolerances between the fiber and the waveguide coupler. The waveguide coupler also features ease of end-facet cleaving. The waveguide coupler can be used in ultra-broadband high coupling efficiency applications or other suitable applications. Single-mode on-chip waveguides incorporating such coupler(s) are also provided, as are methods of manufacturing the waveguide coupler and on-chip waveguide.

An alignment optical measurement element includes a grating coupler, and a reflector coupled to the grating coupler. The alignment optical measurement element is arranged so that: the grating coupler diffracts an incident light in a first direction into a first diffracted light to propagate the first diffracted light as a first propagating light in a second direction, the reflector reflects the first propagating light into a second propagating light in a third direction opposite to the second direction; and the grating coupler diffracts the second propagating light into a second diffracted light to emit the second diffracted light as an emitted light in a fourth direction opposite to the first direction.

An integrated circuit comprises: at least one photonic layer that includes one or more optical waveguides; a first optical coupler that couples at least a first optical mode outside of the photonic layer to a first waveguide in the photonic layer; a photonic device that includes one or more ports in the photonic layer; a first multi-port optical coupler that includes three or more ports in the photonic layer, including a first port optically coupled to the first optical coupler, a second port optically coupled to a first port of the photonic device, and a third port optically coupled to a first optical reflector configured to send substantially all optical power emitted from the third port of the first multi-port optical coupler back to the third port of the first multi-port optical coupler.

There is provided a method for fabricating a vertically tapered spot-size converter on a substrate, comprising: growing a waveguide core on the substrate; coating the waveguide core with a photoresist layer; placing a photomask having patterns at a negative focus offset point with respect to the photoresist layer, the patterns being defined by openings in the photomask, each opening having a cross-section comprising a region of constant width and at least one region of non-constant width, the non-constant width reducing in a direction extending away from the region of constant width; transferring the patterns of the photomask to the photoresist layer; providing the waveguide core with a vertically tapered profile, the vertically tapered profile being provided by the patterns of the photomask; growing a cladding layer over the waveguide core; and patterning and etching the cladding layer and the waveguide core, thereby defining the vertically tapered spot-size converter.

Embodiments may include or relate to an optical coupler. The optical coupler may include a silicon nitride (SiN) waveguide. The waveguide may be formed by placing SiN on an epitaxially grown silicon structure that is then removed subsequent to placement of the SiN. Other embodiments may be described and/or claimed.

A semiconductor wafer includes a semiconductor chip that includes a photonic device. The semiconductor chip includes an optical fiber attachment region in which an optical fiber alignment structure is to be fabricated. The optical fiber alignment structure is not yet fabricated in the optical fiber attachment region. The semiconductor chip includes an in-plane fiber-to-chip optical coupler positioned at an edge of the optical fiber attachment region. The in-plane fiber-to-chip optical coupler is optically connected to the photonic device. A sacrificial optical structure is optically coupled to the in-plane fiber-to-chip optical coupler. The sacrificial optical structure includes an out-of-plane optical coupler configured to receive input light from a light source external to the semiconductor chip. At least a portion of the sacrificial optical structure extends through the optical fiber attachment region.

Disclosed are apparatus and methods for optical coupling. In one example, a described apparatus includes: a planar layer; a grating region comprising an array of scattering elements arranged in the planar layer to form a two-dimensional grating; a first taper structure formed in the planar layer connecting a first side of the grating region to a first waveguide, wherein a shape of the first taper structure is a first triangle that is asymmetric about any line perpendicular to the first side of the grating region in the planar layer; and a second taper structure formed in the planar layer connecting a second side of the grating region to a second waveguide, wherein a shape of the second taper structure is a second triangle that is asymmetric about any line perpendicular to the second side of the grating region in the planar layer, wherein the first side and the second side are substantially perpendicular to each other.