# US 2017/0288370 A1 · High brightness coherent multi-junction diode lasers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0288370 A1 - Document ID: US20170288370A1 - Status: Published application - Kind: A1 - Application number: 15/479,206 - Filed: 2017-04-04 - Published: 2017-10-05 - Earliest claimed: 2016-04-04 - Assignees: nLIGHT, Inc. - Applicants: nLIGHT, Inc. - Inventors: Zhigang Chen; Manoj Kanskar - Web page: https://patentgrep.com/patent/US20170288370A1 ## CPC - H01S 5/3095: {Tunnel junction} - G02B 27/106: {for splitting or combining a plurality of identical beams or images, e.g. image replication} - G02B 27/145: {having sequential partially reflecting surfaces} - H01S 5/4043: {with vertically stacked active layers} - 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 5/02251: using optical fibres - H01S 5/02326: Arrangements for relative positioning of laser diodes and optical components, e.g. grooves in the mount to fix optical fibres or lenses - H01S 5/026: Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers (stabilisation of output H01S5/06) - H01S 5/4012: {Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms} - H01S 5/4018: {Lasers electrically in series} - H01S 5/405: {Two-dimensional arrays} - H01S 5/4068: {with lateral coupling by axially offset or by merging waveguides, e.g. Y-couplers} - H01S 5/4081: {Near-or far field control} - 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 - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract Laser diodes formed on a common substrate with layers of suitable thickness and refractive indices produce output beams that are coherently coupled. A phase mask can be situated to produce phase differences in one or more of the output beams to produce a common wavefront phase. The phase-corrected beams propagate with reduced angular divergence than conventional lasers that are not coherently coupled, and the coherently coupled laser diodes can provide higher beam brightness, enhanced beam parameter product, and superior power coupled into doped fibers in fiber lasers. ## Claims ### Claim 1 A multi-emitter laser diode, comprising: a first active region associated with a lasing wavelength situated between an inner waveguide layer and an outer waveguide layer; a second active region associated with the lasing wavelength situated between an inner waveguide layer and an outer waveguide layer, wherein the inner waveguide layer of the first active region and the inner waveguide layer of the second active region are situated between the first active region and the second active region, and the first active region and the second active region are situated so that an optical beam propagating in the first active region is optically coupled to the second active region. ### Claim 2 (depends on 1) The multi-emitter laser diode of claim 1, wherein at least one of the inner waveguide layers associated with the first and second active regions has a thickness such that the first active region and the second active region are optically coupled. ### Claim 3 (depends on 1) The multi-emitter laser diode of claim 1, wherein the inner waveguide layers associated with the first and second active regions have thicknesses such that the first active region and the second active region are optically coupled. ### Claim 4 (depends on 1) The multi-emitter laser diode of claim 1, wherein the inner waveguides associated with the first and second active regions have a common thickness. ### Claim 5 (depends on 1) The multi-emitter laser diode of claim 1, wherein the inner waveguides associated with the first and second active regions have a combined thickness of less than four times the lasing wavelength. ### Claim 6 (depends on 5) The multi-emitter laser diode of claim 5, wherein the inner waveguides associated with the first and second active regions have a combined thickness of less than the lasing wavelength. ### Claim 7 (depends on 5) The multi-emitter laser diode of claim 5, wherein the inner waveguides associated with the first and second active regions have a combined thickness of less than one-half of the lasing wavelength. ### Claim 8 (depends on 5) The multi-emitter laser diode of claim 5, wherein the inner waveguides associated with the first and second active regions have a combined thickness of less than one-tenth of the lasing wavelength. ### Claim 9 (depends on 1) The multi-emitter laser diode of claim 1, wherein a separation of the first active region and the second active region is less than four times the lasing wavelength. ### Claim 10 (depends on 9) The multi-emitter laser diode of claim 9, wherein the separation the first active region and the second active region is less than the lasing wavelength. ### Claim 11 (depends on 1) The multi-emitter laser diode of claim 1, further comprising a tunnel junction situated between the inner waveguide layer associated with the first active region and the inner waveguide layer associated with the second active region, the tunnel junction situated between a first spacer layer and a second spacer layer situated at the inner waveguide layers associated with the first active region and the second active region, respectively. ### Claim 12 (depends on 11) The multi-emitter laser diode of claim 11, wherein a refractive index difference between at least one of the inner waveguide layer associated with the first active region and the first spacer layer and the inner waveguide layer associated with the second active region and the second first spacer layer is less than 0.5. ### Claim 13 (depends on 12) The multi-emitter laser diode of claim 12, wherein a refractive index difference between the inner waveguide layer associated with the first active region and the first spacer layer and the inner waveguide layer associated with the second active region and the second first spacer layer is less than 0.3. ### Claim 14 (depends on 11) The multi-emitter laser diode of claim 11, wherein a refractive index difference between the inner waveguide layer associated with the first active region and the first spacer layer is less than 0.2 and a refractive index difference between the inner waveguide layer associated with the second active region and the second first spacer layer is less than 0.3. ### Claim 15 (depends on 11) The multi-emitter laser diode of claim 11, wherein the first spacer layer and the second spacer layer have a total thickness that is less than four times the lasing wavelength. ### Claim 16 (depends on 1) The multi-emitter laser diode of claim 1, further comprising a tunnel junction situated between the inner waveguide layer associated with the first active region and the inner waveguide layer associated with the second active region. ### Claim 17 (depends on 16) The multi-emitter laser diode of claim 16, wherein the tunnel junction is adjacent to the inner waveguide layer associated with the first active region and the inner waveguide layer associated with the second active region. ### Claim 18 (depends on 16) The multi-emitter laser diode of claim 16, a refractive index of the inner waveguide layer associated with the first active region is substantially the same as a refractive index of the inner waveguide layer associated with the second active region. ### Claim 19 (depends on 1) The multi-emitter laser diode of claim 1, wherein the inner waveguide layer associated with the first active region and the inner waveguide layer associated with the second active region define a common waveguide. ### Claim 20 (depends on 1) The multi-emitter laser diode of claim 1, wherein the inner and outer waveguide layers associated with the first active region and the inner and outer waveguide layers associated with the second active region define a common waveguide. ### Claim 21 An apparatus, comprising: at least one coherent multi-junction laser diode; and a fast axis collimator situated to collimate an output beam along a fast axis; and a slow axis collimator situated to collimate the output beam along a slow axis. ### Claim 22 (depends on 21) The apparatus of claim 21, wherein the fast axis collimator is situated adjacent the coherent multi-junction laser diode and includes a phase compensation area that produces a 180 degree phase shift between beam portions so as to produce a symmetric mode from an asymmetric mode. ### Claim 23 (depends on 21) The apparatus of claim 21, wherein the slow axis collimator is situated in a beam far field and includes a phase compensation area that produces a 180 degree phase shift between beam portions so as to produce a symmetric mode from an asymmetric mode. ### Claim 24 (depends on 21) The apparatus of claim 21, further comprising a phase compensator situated with respect to the coherent multi-junction laser diode so as to produce a phase shift between optical beams produced by at least two of the multi-junctions. ### Claim 25 (depends on 24) The apparatus of claim 24, wherein the phase mask has phase segments so that the phase shift is 180 degrees. ### Claim 26 (depends on 21) The apparatus of claim 21, wherein the coherent multi-junction laser diode is a coherent double junction laser diode. ### Claim 27 (depends on 21) The apparatus of claim 21, wherein the coherent multi-junction laser diode is selected to produce an antisymmetric mode or a symmetric mode. ### Claim 28 A method of pumping a fiber laser, comprising: producing a coherent beam from a combination of a first optical beam and a second optical beam from a first laser diode and a second laser diode, respectively; adjusting a wavefront phase of at least the first optical beam or the second optical beam; and directing the wavefront phase adjusted beam to a doped optical fiber to produce optical gain in the doped optical fiber. ### Claim 29 (depends on 28) The method of claim 28, wherein the phase is adjusted to produce a symmetric mode or an antisymmetric mode. ### Claim 30 A method of producing a double-emitter laser diode, comprising: defining a first laser diode in at least one or more layers on a substrate; forming a tunnel junction adjacent the first laser diode; and defining a second laser diode in at least one or more layers adjacent the tunnel junction, wherein the first laser diode and the second laser diode are optically coupled so as to produce coherent first and second laser beams. ### Claim 31 (depends on 30) The method of claim 30, wherein the first laser diode and the second laser diode are optically coupled based on at least one of a separation of active regions associated with the first laser diode and the second laser diode and a refractive index difference.