Coherent beam combination system and control method thereof

A method for controlling a coherent beam recombination system configured to provide an output recombined beam, wherein the coherent beam recombination system comprises:

• a laser source providing a source beam having a linewidth;
• a beam broadener coupled to the laser source and configured to provide a broadened beam having a larger linewidth than the source beam;
• a splitter configured to split the broadened beam into a plurality of secondary beams;
• a plurality of channels coupled to the splitter, each channel being configured to receive a respective secondary beam and to provide a respective intermediate beam, each channel comprising an optical amplifier, a phase modulator, an optical delay line, and an opto-mechanical element that provides the respective secondary beam;
• an optical sensor configured to generate a detection signal indicative of an intensity of a received optical beam;
• a focusing optics configured to receive the intermediate beams to provide the output recombined beam from a first portion of each intermediate beam, and to provide a sampled recombined beam to the optical sensor from a second portion of each intermediate beam;
• and
• a control unit,
• the method comprising:
• by a phase-locking module of the control unit:
• providing a plurality of phase control signals, each to the phase modulator of a respective channel;
• receiving the detection signal from the optical sensor, the detection signal being indicative of an intensity of the sampled recombined beam;
• calculating a cost function from the detection signal, the cost function being a function of the intensity of the sampled recombined beam;
• performing an optimization algorithm of the cost function, the optimization algorithm being configured to maximize the intensity of the sample recombined beam;
• and
• providing a plurality of updated phase control signals, based on a result of the optimization algorithm,
• wherein the optical delay lines are variable delay lines, each configured to modify the length of the optical path of the respective channel, the control unit further comprising a delay-equalization module coupled to the channels and the optical sensor, the method further comprising, by the delay-equalization module:
• selecting a channel to be optimized and a reference channel from the plurality of channels;
• determining a coarse estimate of an optical delay between the channel to be optimized and the reference channel, from the detection signal;
• providing a delay-control signal to the optical delay line of the channel to be optimized, based on said coarse estimate;
• determining a fine estimate of the optical delay between the channel to be optimized and the reference channel, from the detection signal;
• updating the delay-control signal, based on said fine estimate.

A method for controlling a coherent beam recombination system configured to provide an output recombined beam, wherein the coherent beam recombination system comprises:

• a laser source providing a source beam having a linewidth;
• a beam broadener coupled to the laser source and configured to provide a broadened beam having a larger linewidth than the source beam;
• a splitter configured to split the broadened beam into a plurality of secondary beams;
• a plurality of channels coupled to the splitter, each channel being configured to receive a respective secondary beam and to provide a respective intermediate beam, each channel comprising an optical amplifier, a phase modulator, an optical delay line, and an opto-mechanical element that provides the respective secondary beam;
• an optical sensor configured to generate a detection signal indicative of an intensity of a received optical beam;
• a focusing optics configured to receive the intermediate beams, to provide the output recombined beam from a first portion of each intermediate beam, and to provide a sampled recombined beam to the optical sensor from a second portion of each intermediate beam;
• and
• a control unit,
• the method comprising:
• by a phase-locking module of the control unit:
• providing a plurality of phase control signals, each to the phase modulator of a respective channel,
• receiving the detection signal from the optical sensor, the detection signal being indicative of an intensity of the sampled recombined beam;
• calculating a cost function from the detection signal, the cost function being a function of the intensity of the sampled recombined beam;
• performing an optimization algorithm of the cost function, the optimization algorithm being configured to maximize the intensity of the sample recombined beam;
• and
• providing a plurality of updated phase control signals, based on a result of the optimization algorithm,
• wherein the coherent beam recombination system further comprises an actuator coupled to the optical sensor, wherein the optical sensor has an active area receiving a spot of the sampled recombined beam, the method further comprising a step of beam steering including controlling, by the actuator, a displacement of the optical sensor, so that the spot of the sampled recombined beam partially falls outside the active area, thereby reducing the intensity of the sampled recombined beam detected by the optical sensor.

A coherent beam recombination system configured to provide an output recombined beam, the coherent beam recombination system comprising:

• a laser source providing a source beam having a linewidth;
• a beam broadener coupled to the laser source and configured to provide a broadened beam having a larger linewidth than the source beam;
• a splitter configured to split the broadened beam into a plurality of secondary beams;
• a plurality of channels coupled to the splitter, each channel being configured to receive a respective secondary beam and to provide a respective intermediate beam, each channel comprising an optical amplifier, a phase modulator, an optical delay line and an opto-mechanical element that provides the respective intermediate beam;
• an optical sensor configured to provide a detection signal indicative of an intensity of a received optical beam;
• a focusing optics configured to receive the intermediate beams, to provide the output recombined beam from a first portion of each intermediate beam, and to provide a sampled recombined beam to the optical sensor from a second portion of each intermediate beam;
• and
• a control unit coupled to the optical sensor and the plurality of channels, wherein the control unit comprises a phase-locking module configured to:
• provide a plurality of phase control signals, each to the phase modulator of a respective channel,
• receive the detection signal from the optical sensor, the detection signal being indicative of an intensity of the sampled recombined beam;
• calculate a cost function from the detection signal, the cost function being a function of the intensity of the sampled recombined beam;
• perform an optimization algorithm of the cost function, the optimization algorithm being configured to maximize the intensity of the sample recombined beam;
• and
• provide a plurality of updated phase control signals, based on a result of the optimization algorithm,
• wherein the coherent beam recombination system further comprises an actuator coupled to the optical sensor and configured to cause a displacement of the optical sensor for steering the output recombined beam.