Spectral beam combination using broad bandwidth lasers
The present invention provides systems and methods for spectral beam combination by applying a spatial chirp to each of a plurality of input beamlets using a respective plurality of dispersive elements and combining the spatially-chirped beamlets into a single collimated output beam using a dispersive element configured to remove the spatial chirp. In an embodiment, each dispersive element is a grating combined with a lens that is confocal to the grating and also confocal to a Fourier plane upon which a transverse distribution of beam spectral components is produced. A final lens-grating pair includes a lens and a grating, where the lens is confocal to the grating and also confocal to the Fourier plane.
1. A method for combining a plurality of laser beamlets to form a single collimated output beam using spectral beam combination, comprising the steps of:
emitting a plurality of laser beamlets from a plurality of broadband laser sources;
applying a spatial chirp to each beamlet using a spatial chirper including at least one dispersive element arranged to produce a transverse distribution of spectral beam components at a Fourier plane; and
combining the spatially-chirped beamlets into a single collimated output beam using a combiner including at least one dispersive element arranged to remove the spatial chirp imposed by said spatial chirper.
2. The method of claim 1 , wherein the spatial chirper includes a plurality of lens-grating pairs, and wherein said step of applying a spatial chirp to each beamlet includes diffracting each beamlet using a grating and focusing each diffracted beamlet on a Fourier plane using a lens.
3. The method of claim 1 , wherein the spatial chirper includes a plurality of grating pairs including first and second gratings, and wherein said step of applying a spatial chirp to each beamlet includes diffracting each beamlet using a first grating of a grating pair and focusing each diffracted beamlet on a Fourier plane using a second grating of a grating pair.
4. The method of claim 1 , wherein the spatial chirper includes a plurality of chirp volume Bragg diffraction cells, and wherein said step of applying a spatial chirp to each beamlet includes diffracting each beamlet using a chip volume Bragg diffraction cell.
5. The method of claim 1 , further comprising actively controlling the position of at least one optical element of the spatial chirper using an active positioning control subsystem so that the beamlets are tiled at the Fourier plane.