Technique for Mitigating Multimode Instabilities in High-Power Large-Mode-Area Fiber Amplifiers

A system for optical amplification includes an optical fiber with a core containing a gain medium surrounded by a cladding, a seed light source, a control light source, and a pump source. The seed light source transmits seed light, at a first wavelength and having a first linewidth greater than 100 MHz, into the core of the fiber. The control light source transmits control light, at a second wavelength shorter than the first wavelength, into the core where it interacts with the pumped gain medium so as to reduce the peak rate of heat deposition per unit length along the fiber. The control light has a second linewidth greater than 100 MHz. The pump source transmits pump light at a pump wavelength, shorter than the second wavelength, into the fiber so as to pump the gain medium and amplify the seed light.