# US 2019/0170936 A1 · Optical coupler having exposed subwavelength gratings for coupling electromagnetic field > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0170936 A1 - Document ID: US20190170936A1 - Status: Published application - Kind: A1 - Application number: 16/185,761 - Filed: 2018-11-09 - Published: 2019-06-06 - Earliest claimed: 2016-11-01 - Assignees: Purdue Research Foundation - Applicants: Purdue Research Foundation - Inventors: Minghao Qi; Min Teng; Kyunghun Han; Sangsik Kim; Ben Niu; Yun Jo Lee - Web page: https://patentgrep.com/patent/US20190170936A1 ## CPC - G02B 6/124: Geodesic lenses or integrated gratings - G02B 5/1809: {with pitch less than or comparable to the wavelength} - G02B 6/1228: {Tapered waveguides, e.g. integrated spot-size transformers (for coupling with fibres G02B6/305)} - G02B 6/305: {and having an integrated mode-size expanding section, e.g. tapered waveguide} - G02B 6/3636: {the mechanical coupling means being grooves (G02B6/3652 takes precedence)} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A semiconductor photonic device includes a substrate, facet(s), and optical coupler(s) associated with the facet(s). Each optical coupler can couple an electromagnetic field incident on the respective facet towards a buried waveguide as the electromagnetic field proceeds into the semiconductor photonic device. In some examples, each coupler has waveguides extending in a longitudinal direction and at least partly encapsulated within a cladding layer. In some examples, at least one waveguide tapers along its length. In some examples, at least one waveguide includes spaced-apart segments arranged to form a subwavelength grating (SWG) configured to entrain electromagnetic radiation. ## Claims ### Claim 1 An optical coupler, comprising: a semiconductor substrate; a first cladding layer arranged at least partly over the semiconductor substrate; a second cladding layer arranged at least partly over the first cladding layer with respect to the semiconductor substrate; a facet in the first cladding layer and in the second cladding layer, the facet extending substantially in a lateral direction; and a plurality of waveguides arranged over the first cladding layer with respect to the semiconductor substrate, wherein the plurality of waveguides comprises: a first waveguide comprising a plurality of first spaced-apart segments arranged substantially along a longitudinal direction; a second waveguide; and a third waveguide spaced farther from the facet longitudinally than at least one of the first waveguide and the second waveguide; and wherein at least two of the waveguides of the plurality of waveguides: are at least partly encapsulated in the second cladding layer; have respective refractive indices higher than a refractive index of the second cladding layer; and are spaced apart from each other along the lateral direction. ### Claim 2 (depends on 1) The optical coupler according to claim 1, wherein: the semiconductor substrate comprises crystalline silicon or a III-V semiconductor; the first cladding layer comprises buried oxide; the second cladding layer comprises silicon oxide; or at least one of the plurality of waveguides comprises silicon. ### Claim 3 (depends on 1) The optical coupler according to claim 1, wherein: at least some of the first spaced-apart segments are arranged to form a subwavelength grating (SWG); the at least some of the first spaced-apart segments have substantially equal extents in the lateral direction and in a third direction that is substantially perpendicular to both the lateral direction and the longitudinal direction; the at least some of the first spaced-apart segments are spaced apart in the longitudinal direction substantially evenly; the at least some of the first spaced-apart segments have substantially equal lengths (L) in the longitudinal direction; and the at least some of the first spaced-apart segments are separated from each other by gaps extending in the longitudinal direction a distance substantially equal to a grating period (Λ) minus the lengths L. ### Claim 4 (depends on 1) The optical coupler according to claim 1, wherein at least: the first waveguide is tapered along at least part of its length; or the third waveguide is tapered along at least part of its length. ### Claim 5 (depends on 1) The optical coupler according to claim 1, wherein the first waveguide has a substantially constant lateral extent along a portion of its length, the portion extending substantially in the longitudinal direction substantially from the facet. ### Claim 6 (depends on 5) The optical coupler according to claim 5, wherein the second waveguide is tapered along a portion of its length, the portion of the length of the second waveguide extending substantially from the facet. ### Claim 7 (depends on 1) The optical coupler according to claim 1, wherein the second waveguide comprises a plurality of second spaced-apart segments arranged substantially along the longitudinal direction. ### Claim 8 (depends on 7) The optical coupler according to claim 7, wherein the second waveguide is tapered along at least a portion of its length. ### Claim 9 (depends on 7) The optical coupler according to claim 7, wherein at least some of the second spaced-apart segments are arranged to form a subwavelength grating (SWG) configured to entrain electromagnetic radiation having a wavelength shorter than one hundred microns. ### Claim 10 (depends on 9) The optical coupler according to claim 9, wherein at least some of the first spaced-apart segments are arranged to form a subwavelength grating (SWG) configured to entrain electromagnetic radiation having the wavelength shorter than one hundred microns. ### Claim 11 (depends on 1) The optical coupler according to claim 1, wherein: the plurality of waveguides further comprises a fourth waveguide spaced apart longitudinally from the facet; the fourth waveguide comprises a plurality of third spaced-apart segments arranged substantially along the longitudinal direction; a longitudinal axis of the fourth waveguide substantially coincides with a longitudinal axis of the fourth waveguide; and the fourth waveguide is arranged longitudinally between the facet and the third waveguide. ### Claim 12 (canceled) ### Claim 13 (depends on 11) The optical coupler according to claim 11, wherein at least some of the third spaced-apart segments are arranged to form a subwavelength grating (SWG) configured to entrain electromagnetic radiation having a wavelength shorter than one hundred microns. ### Claim 14 (depends on 1) The optical coupler according to claim 1, wherein: the semiconductor substrate comprises monocrystalline silicon; the first cladding layer comprises buried oxide; the second cladding layer comprises silicon oxide; or at least one waveguide of the plurality of waveguides comprises silicon nitride. ### Claim 15 (depends on 1) The optical coupler according to claim 1, further comprising an active unit optically connected with the third waveguide. ### Claim 16 (canceled) ### Claim 17 An assembly comprising: a semiconductor photonic device having: a substrate; a plurality of facets; and a plurality of optical couplers associated with respective facets of the plurality of facets; and a plurality of single-mode optical fibers disposed in a splice configuration with respect to respective facets of the plurality of facets; wherein each optical coupler of the plurality of optical couplers comprises: a respective first waveguide spaced apart from the respective facet of the plurality of facets; and means for coupling an electromagnetic field incident on the respective facet towards the respective first waveguide as the electromagnetic field proceeds into the semiconductor photonic device. ### Claim 18 (depends on 17) The assembly according to claim 17, further comprising a V-groove array configured to retain the single-mode optical fibers in position with respect to the respective facets. ### Claim 19 (depends on 17) The assembly according to claim 17, wherein each optical coupler comprises: a respective second waveguide; and a respective third waveguide; wherein the respective second waveguide, the respective first waveguide, and the respective third waveguide of each optical coupler are spaced apart in a lateral direction of that optical coupler; and at least one of the respective second waveguide, the respective first waveguide, and the respective third waveguide of each optical coupler comprises a plurality of segments spaced apart in a longitudinal direction of that optical coupler. ### Claim 20 (depends on 17) The assembly according to claim 17, wherein: the semiconductor photonic device comprises a cladding layer; and the respective first waveguides and the respective second waveguides: are at least partly encapsulated in the cladding layer; and have respective indices of refraction that are higher than an index of refraction of the cladding layer. ### Claim 21 An assembly, wherein: the assembly comprises a semiconductor photonic device having: a plurality of facets; and a plurality of optical couplers associated with respective facets of the plurality of facets; each optical coupler of the plurality of optical couplers comprises: a respective first waveguide; a respective second waveguide spaced apart from the respective facet; and a respective third waveguide; and in each optical coupler: the respective first waveguide, the respective second waveguide, and the respective third waveguide are spaced apart in a lateral direction of that optical coupler; and at least one of the respective first waveguide, the respective second waveguide, and the respective third waveguide comprises a plurality of segments spaced apart in a longitudinal direction of that optical coupler. ### Claim 22 (depends on 21) The assembly according to claim 21, further comprising a plurality of single-mode optical fibers disposed in a splice configuration with respect to respective facets of the plurality of facets.