Method and device for combining laser beams

A method of combining a plurality of input laser beams, of different wavelengths, polarization states of which are predominantly orthogonal to an output beam, comprising:

• using a polarization beam splitter for spatially combining at least two input laser beams of the plurality of input laser beams in mutually orthogonal polarization states, and
• directing the spatially combined at least two input laser beams to a set of birefringent plates, and
• changing a state of polarization of one of the at least two input laser beams relative to the other input laser beam by tilting the set of birefringent plates in such a way that a state of polarization of the output beam becomes predominantly the same for all wavelengths of the output beam, wherein the set of birefringent plates maintains a beam quality parameter M2,
• directing the output beam to a next polarization beam splitter to combine the output beam with a third input laser beam, directing the combined output beam with the third input laser beam to a next set of birefringent plates to perform a spectrally-selective change of light polarization of the third input laser beam relative to the output beam, and repeating for any additional input laser beams.

A device for combining at least a first input laser beam and a second input laser beam with different wavelengths, polarization states of which are predominantly orthogonal, into one output beam, a polarization state of which is predominantly the same for all wavelengths of the output beam, comprising at least one combination of:

• a polarization beam splitter that spatially combines the two input laser beams with different wavelengths whose polarization states are predominantly orthogonal, and
• a successively placed set of birefringent plates mutually oriented at an angle,
• wherein a thickness, a mutual orientation, and a material of the set of birefringent plates provides a change of the polarization of the first input laser beam relative to the second input laser beam in such a way that a state of polarization becomes predominantly the same for all wavelengths of the output beam,
• wherein the set of birefringent plates preserves a beam quality parameter M2.