Method and apparatus for optical beam combination and cleanup using stimulated scattering

An optical beam processing system for producing a diffraction limited output beam, comprising:

• a beam source for providing a divergent input optical beam,
• an elongate beam guiding means, and
• means for coupling said input optical beam from said beam source into said beam guiding means,
• said beam guiding means having guiding parameters capable of supporting substantially multi-mode propagation of said input optical beam, and a length which is long enough to generate a diffraction limited return beam which is substantially more diffraction limited than said input optical beam through stimulated scattering in response to said input optical beam being coupled into said beam guiding means, wherein said stimulated scattering comprises stimulated Brillouin scattering (SBS), and
• wherein said input optical beams are individually low power beams below the SBS threshold of said guiding means but have an aggregate power greater than said SBS threshold, and said input optical beams have respective wavelengths within the SBS linewidth of said beam guiding means.