# US 2019/0317341 A1 · Semiconductor optical amplifier, method for manufacturing same, and optical phase modulator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0317341 A1 - Document ID: US20190317341A1 - Status: Published application - Kind: A1 - Application number: 16/470,441 - Filed: 2017-10-02 - Published: 2019-10-17 - Earliest claimed: 2017-01-10 - Assignees: Mitsubishi Electric Corporation - Applicants: Mitsubishi Electric Corporation - Inventors: Satoshi NISHIKAWA - Web page: https://patentgrep.com/patent/US20190317341A1 ## CPC - G02F 1/01708: {in an optical wavequide structure} - G02F 1/017: Structures with periodic or quasi periodic potential variation, e.g. superlattices, quantum wells - H01S 5/0425: {Electrodes, e.g. characterised by the structure} - H01S 5/1014: {Tapered waveguide, e.g. spotsize converter (H01S5/1064 takes precedence)} - H01S 5/22: having a ridge or stripe structure - H01S 5/343: in AIIIBV compounds, e.g. AlGaAs-laser {, InP-based laser} - H01S 5/4018: {Lasers electrically in series} - H01S 5/5027: {Concatenated amplifiers, i.e. amplifiers in series or cascaded} - G02F 2201/063: ridge; rib; strip loaded - G02F 2202/102: In×P and alloy - G02F 2202/108: quantum wells - G02F 2203/50: Phase-only modulation - G02F 2203/70: Semiconductor optical amplifier [SOA] used in a device covered by G02F - H01S 5/04256: {characterised by the configuration} - H01S 5/1085: {Oblique facets} - H01S 5/227: Buried mesa structure {; Striped active layer} - H01S 5/3434: {with a well layer comprising at least both As and P as V-compounds} - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS - H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL ## Abstract The present invention relates to a semiconductor optical amplifier, the semiconductor optical amplifier including: a plurality of optical amplification regions arranged in series; a passive waveguide region provided between optical amplification regions; and first and second electrodes provided on an upper surface of each of the optical amplification regions. The passive waveguide region electrically insulates between the first electrodes and between the second electrodes of the adjacent optical amplification regions and optically connects the adjacent optical amplification regions. The semiconductor optical amplifier electrically connects the first electrode and the second electrode of the respective adjacent optical amplification regions so that the plurality of optical amplification regions are electrically connected in cascade, and feeds power to the optical amplification regions at both ends of arrangements of the plurality of optical amplification regions thereby driving the plurality of optical amplification regions. ## Claims ### Claim 1 A semiconductor optical amplifier provided on a compound semiconductor substrate, the semiconductor optical amplifier comprising: a plurality of optical amplification regions arranged in series; a passive waveguide region provided between optical amplification regions; and a first electrode and a second electrode provided on an upper surface of each of the optical amplification regions, wherein the passive waveguide region electrically insulates between the first electrodes and between the second electrodes of the adjacent optical amplification regions and optically connects the adjacent optical amplification regions, and wherein the semiconductor optical amplifier electrically connects the first electrode and the second electrode of the respective adjacent optical amplification regions so that the plurality of optical amplification regions are electrically connected in cascade, and feeds power to the optical amplification regions at both ends of arrangements of the plurality of optical amplification regions thereby driving the plurality of optical amplification regions. ### Claim 2 (depends on 1) The semiconductor optical amplifier according to claim 1, wherein the passive waveguide region has a resistance value higher than a forward resistance value when an active layer waveguide in the optical amplification region is driven. ### Claim 3 (depends on 1) The semiconductor optical amplifier according to claim 1, wherein the first electrode is provided on an upper surface of the optical amplification region to cover at least an upper part of the active layer waveguide, and wherein the second electrode is provided on an upper surface of the optical amplification region at a position apart from the active layer waveguide. ### Claim 4 (depends on 3) The semiconductor optical amplifier according to claim 3, wherein the first electrode is provided to extend from above the active layer waveguide to an upper surface of the optical amplification region on a side opposite to the second electrode with the active layer waveguide interposed between the second electrode and the optical amplification region, and wherein the first electrode and the second electrode are provided to be reversely arranged between the adjacent optical amplification regions. ### Claim 5 (depends on 1) The semiconductor optical amplifier according to claim 1, wherein each of the plurality of optical amplification regions has a different region length along an arrangement direction, an optical amplification region having a longest region length is arranged to be closest to a light incident end side of the semiconductor optical amplifier, and an optical amplification region having a shortest region length is arranged to be closest to a light emission end side of the semiconductor optical amplifier. ### Claim 6 (depends on 1) The semiconductor optical amplifier according to claim 1, wherein the plurality of optical amplification regions include an active layer waveguide in a tapered shape in which a width of an active layer waveguide of an optical amplification region arranged closest to a light emission end side of the semiconductor optical amplifier is wider than a width of an active layer waveguide of an optical amplification region arranged closest to a light incident end side. ### Claim 7 (depends on 1) The semiconductor optical amplifier according to claim 1, wherein in the plurality of optical amplification regions, a light confinement coefficient of an active layer waveguide in at least one optical amplification region is different from a light confinement coefficient of an active layer waveguide in another optical amplification region, and wherein an optical amplification region including an active layer waveguide having a smallest light confinement coefficient is arranged closest to a light emission end side of the semiconductor optical amplifier. ### Claim 8 (depends on 7) The semiconductor optical amplifier according to claim 7, wherein an active layer waveguide having a smallest light confinement coefficient has a thickness of an active layer set to be smallest. ### Claim 9 (depends on 1) The semiconductor optical amplifier according to claim 1, further comprising a spot size converter including a transparent waveguide whose waveguide width is reduced in a reverse tapered shape with respect to a traveling direction of light, and wherein the spot size converter is connected to a light emission end of the semiconductor optical amplifier. ### Claim 10 (depends on 1) A method for manufacturing the semiconductor optical amplifier according to claim 1, the method comprising: forming a multilayer film of a compound semiconductor including an active layer on the compound semiconductor substrate, and then removing the multilayer film in a region forming the passive waveguide region; and forming a transparent waveguide to be butt-joint coupled with the active layer waveguide by butt joint growth in a region from which the multilayer film is removed to form the passive waveguide region. ### Claim 11 (depends on 1) A method for manufacturing the semiconductor optical amplifier according to claim 1, the method comprising: forming a multilayer film of a compound semiconductor including an active layer on the compound semiconductor substrate and then selectively implanting protons or helium ions into the multilayer film in a region in which the passive waveguide region is formed, and forming an ion implantation region in the active layer and a multilayer film of the compound semiconductor above and below the active layer to form the passive waveguide region. ### Claim 12 (depends on 1) An optical phase modulator comprising: a QPSK phase modulator configured to split incident light into a first demultiplexed light beam and a second demultiplexed light beam, configured to split the first demultiplexed light beam into a third demultiplexed light beam and a fourth demultiplexed light beam, configured to split the second demultiplexed light beam into a fifth demultiplexed light beam and a sixth demultiplexed light beam, configured to modulate at least one of the third demultiplexed light beam and the fourth demultiplexed light beam and then to multiplex the demultiplexed light beams to form I modulated light, configured to modulate at least one of the fifth demultiplexed light beam and the sixth demultiplexed light beam and then to multiplex the demultiplexed light beams to form Q modulated light, configured to multiplex the I modulated light and Q modulated light to generate QPSK modulated light; and an output side semiconductor optical amplifier configured to amplify emission light of the QPSK phase modulator, wherein the output side semiconductor optical amplifier includes the semiconductor optical amplifier according to claim 1, and wherein the QPSK phase modulator is provided on a same compound semiconductor substrate as that of the output side semiconductor optical amplifier. ### Claim 13 (depends on 12) The optical phase modulator according to claim 12, further comprising an input side semiconductor optical amplifier provided on an optical input side of the QPSK phase modulator, the input side semiconductor optical amplifier configured to amplify incident light to input the amplified light into the QPSK phase modulator. ### Claim 14 (depends on 12) An optical phase modulator comprising the optical phase modulator according to claim 12 as first and second optical phase modulators, wherein the optical phase modulator splits incident light into beams and inputs the beams to the first and second optical phase modulators, and outputs respective signal light beams from the first and second optical phase modulators. ### Claim 15 (depends on 12) An optical phase modulator comprising: a first and second optical phase modulators including the optical phase modulator according to claim 12; and an input side semiconductor optical amplifier configured to amplify incident light to input the amplified light into the first and second optical phase modulators, wherein the optical phase modulator splits emission light of the input side semiconductor optical amplifier into beams and inputs the beams to the first and second optical phase modulators, and outputs respective signal light beams from the first and second optical phase modulators. ### Claim 16 (depends on 13) The optical phase modulator according to claim 13, wherein power is supplied in parallel to at least two semiconductor optical amplifiers of a plurality of semiconductor optical amplifiers. ### Claim 17 (depends on 14) The optical phase modulator according to claim 14, wherein power is supplied in parallel to at least two semiconductor optical amplifiers of a plurality of semiconductor optical amplifiers. ### Claim 18 (depends on 15) The optical phase modulator according to claim 15, wherein power is supplied in parallel to at least two semiconductor optical amplifiers of a plurality of semiconductor optical amplifiers.