# US 2020/0403383 A1 · Semiconductor amplifier with low polariation-dependent gain > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0403383 A1 - Document ID: US20200403383A1 - Status: Published application - Kind: A1 - Application number: 16/904,491 - Filed: 2020-06-17 - Published: 2020-12-24 - Earliest claimed: 2019-06-19 - Assignees: NEC Laboratories America, Inc. - Applicants: NEC Laboratories America, Inc. - Inventors: Fatih YAMAN; Shinsuke FUJISAWA; Eduardo Mateo RODRIGUEZ; Kohei NAKAMURA; Takanori INOUE; Yoshihisa INADA; Takaaki OGATA - Web page: https://patentgrep.com/patent/US20200403383A1 ## CPC - H01S 5/5018: {using two or more amplifiers or multiple passes through the same amplifier} - H01S 3/10061: {Polarization control} - H01S 5/0064: {Anti-reflection components, e.g. optical isolators} - H01S 5/5036: {the arrangement being polarisation-selective} - H01S 3/06754: {Fibre amplifiers (H01S3/06708 takes precedence)} - H01S 5/005: {Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping (H01S5/026, H01S5/18388 take precedence)} - H01S 5/5027: {Concatenated amplifiers, i.e. amplifiers in series or cascaded} - 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 Aspects of the present disclosure describe systems, methods and structures for providing semiconductor amplifiers exhibiting a low polarization-dependent gain. ## Claims ### Claim 1 A semiconductor optical amplifier module exhibiting low polarization dependent gain characteristics, said module comprising: an input port for receiving a dual-polarization signal and an output port for outputting an amplified dual-polarization signal; an optical circulator in optical communication with the input port, the output port, and a polarization beam splitter/combiner, said circulator configured to direct optical signals between the input port, the output port, and the polarization beam splitter/combiner; and a pair of semiconductor optical amplifiers, each having a first port and a second port, the first port of each optically connected to the polarization beam splitter combiner, and the second port of each optically connected to one another. ### Claim 2 (depends on 1) The module of claim 1 configured such that an H polarization of the dual-polarization signal is amplified by one of the semiconductor optical amplifiers traversing that amplifier in a first direction and amplified by the other one of the semiconductor optical amplifiers traversing that other amplifier in an opposite direction. ### Claim 3 (depends on 2) The module of claim 2 configured such that an V polarization of the dual-polarization signal is amplified by one of the semiconductor optical amplifiers traversing that amplifier in a first direction and amplified by the other one of the semiconductor optical amplifiers traversing that other amplifier in an opposite direction. ### Claim 4 (depends on 1) The module of claim 1 further comprising: an optical pigtail, connecting the second port of each optical amplifier to one another. ### Claim 5 (depends on 4) The module of claim 4 wherein the optical pigtail introduces a transmission delay in optical signals from one semiconductor optical amplifier to the other semiconductor optical amplifier, said transmission delay configured such that it is longer than a carrier lifetime of the semiconductor optical amplifiers. ### Claim 6 An improved optical amplifier module exhibiting low polarization dependent gain comprising: an input port for receiving a dual-polarization signal and an output port for outputting an amplified dual-polarization signal; an optical circulator in optical communication with the input port, the output port, and a dual-polarization semiconductor optical amplifier, said circulator configured to direct optical signals between the input port, the output port, and the dual-polarization semiconductor optical amplifier; the dual-polarization semiconductor optical amplifier having a first port and a second port, the first port optically connected to the optical circulator, the second port optically connected to a Faraday mirror; and the Faraday mirror. ### Claim 7 (depends on 6) The improved optical amplifier module according to claim 6 wherein the Faraday mirror is configured to rotate polarizations of optical signals directed thereto by the dual-polarization semiconductor optical amplifier by substantially 90 degrees before reflecting the rotated polarization signals back to the dual-polarization semiconductor optical amplifier. ### Claim 8 A method of operating a semiconductor optical amplifier module having an input port for receiving dual-polarization optical signals and an output port for outputting amplified, dual-polarization signals, the METHOD CHARACTERIZED IN THAT: the dual-polarization optical signals are directed though a semiconductor optical amplifier at least twice, at least once in a first direction, and at least once in a second direction, wherein the second direction is opposite to the first direction. ### Claim 9 (depends on 8) The method of claim 8 FURTHER CHARACTERIZED IN THAT: the dual-polarization optical signals are reflected by a Faraday mirror after being directed through the semiconductor optical amplifier the first time, but before being directed through the semiconductor optical amplifier the second time. ### Claim 10 (depends on 9) The method of claim 9 FURTHER CHARACTERIZED IN THAT: the Faraday mirror rotates individual polarizations of the dual-polarization optical signals by substantially 90 degrees upon reflection thereby. ### Claim 11 (depends on 8) The method of claim 8 FURTHER CHARACTERIZED IN THAT: the dual-polarization optical signals include an H polarization and a V polarization, the semiconductor optical amplifier includes first and second individual semiconductor optical amplifiers wherein the H polarization is amplified by the first semiconductor optical amplifier while traversing it in a first direction, and then amplified by the second semiconductor optical while traversing it in a second direction, wherein the second direction is opposite to the first direction, the Y polarization is amplified by the second semiconductor optical amplifier while traversing it in a third direction, and then amplified by the first semiconductor optical while traversing it in a fourth direction, wherein the fourth direction is opposite to the third direction.