# US 2018/0026418 A1 · Coherent Combining Pulse Bursts In Time Domain > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0026418 A1 - Document ID: US20180026418A1 - Status: Published application - Kind: A1 - Application number: 15/724,723 - Filed: 2017-10-04 - Published: 2018-01-25 - Earliest claimed: 2013-12-19 - Assignees: The Regents of the University of Michigan - Applicants: The Regents of the University of Michigan - Inventors: Almantas GALVANAUSKAS - Web page: https://patentgrep.com/patent/US20180026418A1 ## CPC - H01S 3/1062: {using a controlled passive interferometer, e.g. a Fabry-Perot etalon} - H01S 3/005: {Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping (shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B)} - H01S 3/1307: {Stabilisation of the phase} - H01S 3/23: Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media - H01S 3/2308: {Amplifier arrangements, e.g. MOPA} - H01S 3/2383: {Parallel arrangements} - G02B 27/1006: {for splitting or combining different wavelengths (G02B27/1086, G02B27/141 take precedence)} - 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 A beam combining and pulse stacking technique is provided that enhances laser pulse energy by coherent stacking pulse bursts (i.e. non-periodic pulsed signals) in time domain. This energy enhancement is achieved by using various configurations of Fabry-Perot, Gires-Tournois and other types of resonant cavities, so that a multiple-pulse burst incident at either a single input or multiple inputs of the system produces an output with a solitary pulse, which contains the summed energy of the incident multiple pulses from all beams. This disclosure provides a substantial improvement over conventional coherent-combining methods in that it achieves very high pulse energies using a relatively small number of combined laser systems, thus providing with orders of magnitude reduction in system size, complexity, and cost compared to current combining approaches. ## Claims ### Claim at position 1 -18. (canceled) ### Claim 19 A system for coherently combining pulses of a pulsed optical signal in the time domain, comprising: a first combining stage configured to receive an optical input signal and comprised of one or more resonant cavities arranged in a sequential manner with each other, wherein the optical input signal has one or more clusters of pulses in a pulse train, such that amplitude and phase of pulses in the one or more clusters varies amongst pulses, and wherein each resonant cavity in the first combining stage has an entirely reflective cavity and operates to coherently combine pulses in the one or more clusters in the time domain to form an output signal; and a second combining stage configured to receive the output signal from the first combining stage and comprised of one or more resonant cavities arranged in a sequential manner with each other, wherein each resonant cavity in the second combining stage has an entirely reflective cavity and operates to coherently combine pulses in the output signal in the time domain. ### Claim 20 (depends on 19) The system of claim 19 wherein each of the one or more resonant cavities in the first combining stage exhibit same round-trip time. ### Claim 21 (depends on 20) The system of claim 20 wherein the round-trip time exhibited by the one or more resonant cavities in the first combining stage is a multiple of repetition period between pulses in the pulse train. ### Claim 22 (depends on 19) The system of claim 19 wherein each of the one or more resonant cavities in the first combining stage exhibit a round-trip time having a first value and each of the one or more resonant cavities in the second combining stage exhibit a round-trip time having a second value, such that the first value differs from the second value. ### Claim 23 (depends on 19) The system of claim 19 wherein reflectivity differs amongst the one or more resonant cavities in the first combining stage and reflectivity differs amongst the one or more resonant cavities in the second combining stage. ### Claim 24 (depends on 19) The system of claim 19 wherein round-trip phase differs amongst the one or more resonant cavities in the first combining stage and round-trip phase differs amongst the one or more resonant cavities in the second combining stage. ### Claim 25 (depends on 19) The system of claim 19 wherein number of resonant cavities in the first combining stage differs from number of resonant cavities in the second combining stage. ### Claim 26 (depends on 19) The system of claim 19 wherein the resonant cavities in the first combining stage and the second combining stage are Gires-Tournois interferometers. ### Claim 27 A method for coherently combining pulses of a pulsed optical signal in the time domain, comprising: receiving an optical input signal comprised of a periodic pulse train; amplitude modulating the optical input signal to form one or more clusters of pulses, such that amplitude of pulses in each cluster varies amongst pulses; phase modulating the optical input signal, such that phase of pulses in each cluster varies amongst pulses; and coherently combining pulses in the at least one cluster in the time domain to form an optical signal with a solitary pulse using a plurality of resonant cavities arranged in a sequential manner. ### Claim 28 (depends on 27) The method of claim 27 further comprises arranging the plurality of resonant cavities into two or more combining stages, where each stage includes at least one resonant cavity in the plurality of resonant cavities. ### Claim 29 (depends on 28) The method of claim 28 wherein each resonant cavity in a given combining stage exhibits same round-trip time. ### Claim 30 (depends on 29) The method of claim 29 wherein the round-trip time exhibited by the one or more resonant cavities in the given combining stage is a multiple of repetition period between pulses in the pulse train ### Claim 31 (depends on 28) The method of claim 28 wherein each of the resonant cavities in a first combining stage exhibit a round-trip time having a first value and each of the resonant cavities in a second combining stage exhibit a round-trip time having a second value, such that the first value differs from the second value. ### Claim 32 (depends on 31) The system of claim 31 wherein at least one of reflectivity differs amongst the one or more resonant cavities in the first combining stage or reflectivity differs amongst the one or more resonant cavities in the second combining stage. ### Claim 33 (depends on 31) The system of claim 31 wherein at least one of round-trip phase differs amongst the one or more resonant cavities in the first combining stage or round-trip phase differs amongst the one or more resonant cavities in the second combining stage. ### Claim 34 (depends on 31) The system of claim 31 wherein number of resonant cavities in the first combining stage differs from number of resonant cavities in the second combining stage. ### Claim 35 (depends on 27) The method of claim 27 further comprises coherently combining pulses in each cluster of pulses using a Gires-Tournois interferometer. ### Claim 36 (depends on 27) The method of claim 27 further comprises amplifying the optical input signal before the step of coherently combining pulses. ### Claim 37 A method for coherently combining pulses of a pulsed optical signal in the time domain, comprising: receiving an optical input signal comprised of a periodic pulse train; forming at least one cluster of pulses in the pulse train, where amplitude and phase of pulses in the at least one cluster varies amongst pulses; and coherently combining pulses in the at least one cluster in the time domain to form an optical signal with a solitary pulse using optical delay lines. ### Claim 38 (depends on 37) The method of claim 37 wherein forming at least one cluster of pulses further comprises amplitude modulating the optical input signal and phase modulating the optical input signal.