# US 2019/0170944 A1 · Multistage spot size converter in silicon photonics > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0170944 A1 - Document ID: US20190170944A1 - Status: Published application - Kind: A1 - Application number: 16/171,132 - Filed: 2018-10-25 - Published: 2019-06-06 - Earliest claimed: 2017-10-25 - Assignees: Skorpios Technologies, Inc. - Applicants: Skorpios Technologies, Inc. - Inventors: Majid Sodagar; Stephen B. Krasulick; John Zyskind; Paveen Apiratikul; Luca Cafiero - Web page: https://patentgrep.com/patent/US20190170944A1 ## CPC - G02B 6/305: {and having an integrated mode-size expanding section, e.g. tapered waveguide} - G02B 2006/12061: {Silicon} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A device is provided for optical mode spot size conversion to optically couple a semiconductor waveguide with an optical fiber. The device includes a waveguide comprising a waveguide taper region, which comprises a shoulder portion and a ridge portion above the shoulder portion. The ridge portion has a width that tapers to meet a width of the shoulder portion. The waveguide taper region comprises a first material. The device also has a mode converter coupled to the waveguide. The mode converter includes a plurality of stages, and each of the plurality of stages tapers in a direction similar to a direction of taper of the waveguide taper region. The mode converter is made of a second material different from the first material. ## Claims ### Claim 1 A device for optical mode spot size conversion to optically couple a semiconductor waveguide with an optical fiber, the device comprising: a waveguide comprising a waveguide taper region, wherein: the waveguide taper region comprises a shoulder portion and a ridge portion above the shoulder portion, the ridge portion having a width that tapers to meet a width of the shoulder portion; and the waveguide taper region comprises a first material; and a mode converter coupled to the waveguide, wherein: the mode converter comprises a plurality of stages; each of the plurality of stages tapers in a direction similar to a direction of taper of the waveguide taper region; and the mode converter is made of a second material different from the first material. ### Claim 2 (depends on 1) The device of claim 1, wherein: the mode converter comprises a first stage and a second stage of the plurality of stages, the second stage overlying the first stage; the first stage comprises a first portion that does not taper and a second portion that tapers; and the second stage extends over the first portion and the second portion of the first stage. ### Claim 3 (depends on 2) The device of claim 2, wherein the first portion of the first stage of the mode converter and the shoulder portion of the waveguide have a common width. ### Claim 4 (depends on 1) The device of claim 1, wherein the waveguide further comprises a waveguide extension region coupled between the waveguide taper region and the mode converter, wherein: the waveguide extension region is made of the first material; the waveguide extension region has a thickness equal to a combined thickness of the shoulder portion and the ridge portion of the waveguide taper region; and the waveguide extension region and the shoulder portion of the waveguide taper region have a common width. ### Claim 5 (depends on 4) The device of claim 4, wherein the waveguide extension region has a common thickness as the waveguide taper region and a first stage of the mode converter. ### Claim 6 (depends on 4) The device of claim 4, wherein the waveguide extension region has a common width as an output end of the waveguide taper region and an input end of a first stage of the mode converter. ### Claim 7 (depends on 1) The device of claim 1, wherein the number of stages in the mode converter is greater than three and less than eleven. ### Claim 8 (depends on 1) The device of claim 1, wherein the number of stages in the mode converter is seven. ### Claim 9 (depends on 1) The device of claim 1, wherein the ridge portion tapers from a narrower width of 0.75-2.75 μm near an input end to a wider width of 2.0-4.5 μm near an output end. ### Claim 10 (depends on 1) The device of claim 1, wherein, at an output end of the mode converter, the mode converter has a rectangular cross-section, and the plurality of stages has a common maximum width. ### Claim 11 (depends on 1) The device of claim 1, wherein: the mode converter comprises a first stage and a second stage of the number of stages, the first stage has a first maximum width, the second stage has a second maximum width, and the first maximum width of the first stage is greater than the second maximum width of the second stage. ### Claim 12 (depends on 1) The device of claim 1, wherein: at a cross section of the mode converter at an output end of the device, each stage of the plurality of stages has a different width; and a first stage of the plurality of stages, which is closer to the shoulder portion, has a wider width than a second stage of the plurality of stages, which is farther from the shoulder portion than the first stage. ### Claim 13 (depends on 12) The device of claim 12, wherein: the first stage of the mode converter has a first length, the second stage of the mode converter has a second length, and the first length is equal to the second length. ### Claim 14 (depends on 1) The device of claim 1, wherein: the waveguide taper region comprises crystalline silicon in a device layer disposed on a buried-oxide layer of an SOI (silicon-on-insulator) substrate; and the mode converter comprises non-crystalline silicon formed on the buried-oxide layer of the SOI substrate. ### Claim 15 A method, for converting optical mode spot size between a semiconductor waveguide and an optical fiber, the method comprising: receiving a light beam at a waveguide comprising a waveguide taper region, the waveguide taper region comprising a shoulder portion and a ridge portion above the shoulder portion, the ridge portion having a width that tapers to meet a width of the shoulder portion, the waveguide taper region comprising a first material; expanding an optical mode of the light beam in the waveguide taper region; coupling the light beam from the waveguide taper region to a mode converter, wherein: the mode converter comprises a plurality of stages; each of the plurality of stages tapers in a direction similar to a direction of taper of the waveguide taper region; and the mode converter is made of a second material different from the first material; expanding the light beam through each of the plurality of stages in the mode converter; and coupling the light beam to the optical fiber. ### Claim 16 (depends on 15) The method of claim 15, further comprising transmitting the light beam through a first stage of the mode converter to a second stage, wherein: the first stage comprises a first portion that does not taper and a second portion that tapers; and the second stage extends over the first portion and the second portion of the first stage. ### Claim 17 (depends on 15) The method of claim 15, further comprising transmitting the light beam through a waveguide extension region coupled between the waveguide taper region and the mode converter, wherein: the waveguide extension region is made of the first material; the waveguide extension region has a thickness equal to a combined thickness of the shoulder portion and the ridge portion of the waveguide taper region; and the waveguide extension region and the shoulder portion of the waveguide taper region have a common width. ### Claim 18 A device for optical mode spot size conversion to optically couple a semiconductor waveguide with an optical fiber, the device comprising: a waveguide comprising a waveguide taper region and a waveguide extension region coupled to the waveguide taper region, wherein: the waveguide taper region comprises a shoulder portion and a ridge portion above the shoulder portion, the ridge portion having a width that tapers to meet a width of the shoulder portion; and the waveguide taper region is made of a first material; the waveguide extension region is made of the first material; the waveguide extension region has a thickness equal to a combined thickness of the shoulder portion and the ridge portion of the waveguide taper region; and the waveguide extension region and the shoulder portion of the waveguide taper region have a common width; and a mode converter coupled to the waveguide extension region, wherein: the mode converter comprises a plurality of stages; each of the plurality of stages tapers in a direction similar to a direction of taper of the waveguide taper region; the mode converter comprises a first stage and a second stage of the plurality of stages, the first stage comprising a first portion that does not taper and a second portion that tapers; and the second stage extends over the first portion and the second portion of the first stage; and the mode converter is made of a second material different from the first material. ### Claim 19 (depends on 18) The device of claim 18, wherein the ridge portion tapers from a narrower width of 0.75-2.75 μm near an input end to a wider width of 2.0-4.5 μm near an output end. ### Claim 20 (depends on 18) The device of claim 18, wherein the waveguide extension region has a common thickness as the waveguide taper region and the first stage of the mode converter.