# US 10,312,657 B2 · 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 10,312,657 B2 - Document ID: US10312657B2 - Status: Granted - Kind: B2 - Application number: 15/724,723 - Filed: 2017-10-04 - Published: 2018-01-25 - Granted: 2019-06-04 - 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/US10312657B2 ## 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 1 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 each of the one or more clusters of pulses 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 2 (depends on 1) The method of claim 1 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 3 (depends on 2) The method of claim 2 wherein each resonant cavity in a given combining stage exhibits same round-trip time. ### Claim 4 (depends on 3) The method of claim 3 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 5 (depends on 2) The method of claim 2 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 6 (depends on 5) The system of claim 5 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 7 (depends on 5) The system of claim 5 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 8 (depends on 5) The system of claim 5 wherein number of resonant cavities in the first combining stage differs from number of resonant cavities in the second combining stage. ### Claim 9 (depends on 1) The method of claim 1 further comprises coherently combining pulses in each cluster of pulses using a Gires-Tournois interferometer. ### Claim 10 (depends on 1) The method of claim 1 further comprises amplifying the optical input signal before the step of coherently combining pulses. ### Claim 11 (depends on 1) The method of claim 1 further comprises coherently combining pulses in each cluster of pulses using optical delay lines. ### Claim 12 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 each of the one or more clusters of pulses in the time domain to form an optical signal with a solitary pulse using optical delay lines.