Patent ID: 6894828

Claim:
An amplifier for a laser beam that has a wavelength (λ), comprising: a multi-mode, self-imaging waveguide having a core comprising a gain or mixing medium with an index of refraction (n) and a core length extending between a core entrance face and a core exit face, said core also having a rectangular cross-section that provides a waveguide width (a), which is large enough to support and propagate multiple modes of the laser beam and a waveguide self-imaging period (WSIP) defined as a distance in the multi-mode waveguide in which a profile or image of the laser beam is periodically re-imaged, wherein WSIP=4na 2 /λ in general for the laser beam propagating through the core and WSIP=na 2 /λ when the laser beam is perfectly symmetric with respect to the center of the waveguide, and wherein said core is such that the laser beam propagating through the core from the core entrance fact to the core exit face has an optical path length with a numerical aperture and an exit face that is a non-zero integer multiple of the waveguide self-imaging period (WISP); a beam input coupling system capable of providing the profile or image of the laser beam with a TEM 00 wavefront at the core entrance face within the numerical aperture of the core entrance face to propagate the laser beam into and through the waveguide to the exit face; and a pump light source coupled into the waveguide core medium to propagate pump light energy into the core medium to be extracted by the laser beam.