Error control for high-power laser system employing diffractive optical element beam combiner with tilt error control

A laser system comprising:

• a master oscillator;
• a plurality of amplifiers, each optically coupled to the master oscillator and each producing, responsive to a signal therefrom, a respective monochromatic beamlet, each monochromatic beamlet contributing a respective beamlet error,
• a diffractive optical element optically coupled via a converging lens to each of the plurality of amplifiers to receive said respective monochromatic beamlet therefrom, wherein said monochromatic beamlets are converged on the diffractive optical element via the converging lens, said diffractive optical element producing a combined output beam responsive to said monochromatic beamlets, said combined output beam exhibiting a combined error characteristic resulting from said beamlet errors;
• and
• an error control system adapted to:
• measure from a sample of said combined output beam one of said beamlet errors contributed by a specific one of said monochromatic beamlets as distinct from said beamlet errors contributed by all other monochromatic beamlets and to adjust a characteristic of said one specific monochromatic beamlet so as to substantially minimize said one beamlet error;
• define one of said monochromatic beamlets as a reference beamlet;
• and
• for each of said monochromatic beamlets other than said reference beamlet, tag such beamlet with an identifying signal before such beamlet is combined with other beamlets, such that after all beamlets are combined, an error characteristic contributed by such beamlet is measurable distinctly from error contributions contributed by all other beamlets.

A laser system comprising:

• a master oscillator;
• a plurality of amplifiers, each optically coupled to the master oscillator and each producing, responsive to a signal therefrom, a respective monochromatic beamlet, each monochromatic beamlet contributing a respective beamlet tilt error;
• a diffractive optical element optically coupled via a converging lens to each of the plurality of amplifiers to receive said respective monochromatic beamlet therefrom, wherein said monochromatic beamlets are converged on the diffractive optical element via the converging lens, said diffractive optical element producing a combined output beam responsive to said monochromatic beamlets, said combined output beam exhibiting a combined error characteristic resulting from said beamlet errors;
• and
• a tilt error control system adapted to measure from a sample of said combined output beam a beamlet tilt error contributed by a specific one of said monochromatic beamlets as distinct from beamlet tilt errors contributed by all other monochromatic beamlets and to adjust an entry angle characteristic of said specific one beamlet so as to minimize said contributed beamlet tilt error.

A method for controlling an error characteristic in a laser system comprising the steps of:

• tagging a plurality of monochromatic beamlets produced by laser amplifiers prior to beam combination via a converging lens with an identification tag;
• sampling a combined output beam resulting from combining said plurality of monochromatic beamlets;
• from said sampled combined output beam, measuring a tilt error affecting one of said beamlets distinct from tilt errors affecting any other of said beamlets;
• generating an error correction signal to reduce said tilt error of one of said beamlets responsive to said measured tilt error;
• and
• adjusting a physical characteristic of said one beamlet accordingly to reduce the tilt error.