# US 11,079,549 B2 · 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 11,079,549 B2 - Document ID: US11079549B2 - Status: Granted - Kind: B2 - Application number: 16/839,826 - Filed: 2020-04-03 - Published: 2020-12-24 - Granted: 2021-08-03 - 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/US11079549B2 ## 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 method for manufacturing a device for optical mode spot size conversion, the method comprising: providing a substrate having a device layer disposed on the substrate, wherein the device layer comprises a first material; etching the device layer to form a waveguide; etching the device layer to form a waveguide taper region, wherein: the waveguide taper region comprises a shoulder portion and a ridge portion, the ridge portion oriented along a direction of beam propagation, the ridge portion having a width that tapers to meet a width of the shoulder portion; and forming a mode converter coupled with the waveguide taper 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 ridge portion 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 method claim 1, wherein the ridge portion of the waveguide taper region is disposed directly above the shoulder portion of the waveguide. ### Claim 3 (depends on 1) The method claim 1, further comprising: applying a photoresist on the device layer; etching the device layer to form a first recess, the first recess having a shape of a first pattern; removing photoresist from the device layer; filling the first recess with a second material different from the first material; etching the device layer to define the waveguide, and etching the second material to form a first stage of the mode converter, such that the first stage of the mode converter is aligned with the waveguide; covering the substrate with a first cladding; applying photoresist on the first cladding; etching the first cladding to form a second recess, the second recess having a shape of a second pattern; removing photoresist from the first cladding; and filling the second recess with the second material to forms a second stage of the mode converter. ### Claim 4 (depends on 3) The method claim 3, wherein: the waveguide taper region comprises crystalline silicon in the 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 5 (depends on 3) The method claim 3, wherein etching the first cladding uses a highly selective etch such that the first cladding is more easily etched than the first material and the second material. ### Claim 6 (depends on 3) The method claim 3, wherein: the first stage of the mode converter comprises a first portion that does not taper and a second portion that tapers; and the second stage of the mode converter extends over the first portion and the second portion of the first stage. ### Claim 7 (depends on 6) The method claim 6, wherein the first portion of the first stage of the mode converter and the shoulder portion of the waveguide have a common width. ### Claim 8 (depends on 3) The method claim 3, further comprising: applying a second cladding on the second stage of the mode converter; etching the second cladding to form a third recess, the third recess having a shape of a third pattern; and filling the third recess with additional second material to form a third stage of the mode converter. ### Claim 9 (depends on 8) The method claim 8, wherein the number of stages in the mode converter is seven. ### Claim 10 (depends on 1) The method 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 from the device layer; 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 11 (depends on 10) The method claim 10, wherein the waveguide extension region has a common thickness as the waveguide taper region and a first stage of the mode converter. ### Claim 12 (depends on 10) The method claim 10, 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 13 A method for manufacturing a device for optical mode spot size conversion, the method comprising: providing a substrate having a device layer disposed on the substrate, the device layer comprising a first material; etching the device layer to form a waveguide and a first stage of a mode converter coupled to the waveguide, wherein the waveguide comprises a waveguide taper region having a shoulder portion and a ridge portion, the ridge portion disposed directly above the shoulder portion and oriented along a direction of beam propagation, the ridge portion having a width that tapers to meet a width of the shoulder portion; depositing a cladding layer over the substrate; forming a first cladding on the device layer; applying photoresist on the first cladding; etching the first cladding to form a first recess, the first recess having a shape of a first pattern; removing photoresist from the first cladding; filling the first recess with a second material to form a second stage of the mode converter. ### Claim 14 (depends on 13) The method of claim 13, wherein the first material is crystalline silicon and the second material is non-crystalline silicon. ### Claim 15 (depends on 13) The method of claim 13, wherein the device layer comprises crystalline silicon disposed on a buried-oxide layer of an SOI (silicon-on-insulator) substrate. ### Claim 16 (depends on 13) The method of claim 13, wherein the waveguide further comprises a waveguide extension region coupled between the waveguide taper region and the mode converter. ### Claim 17 (depends on 16) The method of claim 16, wherein: 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 method for manufacturing a device for optical mode spot size conversion, the method comprising: providing a substrate having a device layer disposed on the substrate, wherein the device layer comprises a first material; etching the device layer to form a waveguide and a waveguide extension region; etching the device layer to form a waveguide taper region, the waveguide taper region coupled to the waveguide extension region, wherein: the waveguide taper region comprises a shoulder portion and a ridge portion, the ridge portion having a width that tapers to meet a width of the shoulder portion; and 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 forming 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 ridge portion 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 method of claim 18, wherein the ridge portion of the waveguide taper region 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 method 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.