Abstract: This disclosure enables laser-based gain elements, such as fiber lasers, fiber amplifiers, and the like, that have higher power and better frequency stability than can be achieved in the prior art. Embodiments disclosed herein include a fiber-based gain element having a first portion in which anti-Stokes fluorescence (ASF) reduces its temperature below that of an ambient environment and a second portion whose temperature is not reduced below that of the ambient environment. The fiber-based gain element is arranged such that the first and second portions are thermally coupled so heat can flow from the second portion into the first portion, thereby reducing the average temperature of the gain element. In some embodiments, a core configured to provide optical gain is thermally coupled with a first cladding configured to exhibit ASF cooling via an intervening cladding layer that acts to confine a first pump signal to the core.