Patent ID: 8761211

Claim:
A light amplifier for amplifying light from a near-diffraction-limited laser source, the light amplifier comprising: a length of multi-mode optical fiber, said multi-mode optical fiber including a gain medium; a length of single-mode optical fiber optically coupled to the length of multi-mode optical fiber, a fundamental mode of said multi-mode fiber matched to the mode of the single mode fiber, an energy source for exciting said gain medium, said energy source arranged for side pumping said optical fiber, and an input optically coupled to said multi-mode fiber, said input comprising a near-diffraction-limited laser source providing a nearly diffraction limited input beam having a signal wavelength, said input comprising said length of single-mode optical fiber, said multi-mode fiber providing an output beam having the signal wavelength that is amplified by said gain medium, wherein said output beam having the signal wavelength is substantially in the fundamental mode at an output of said light amplifier, wherein said light amplifier is configured to provide a peak output power greater than 10 KW for the output beam having the signal wavelength.