3-Level Ytterbium Fiber Lasers for Efficient High-Power Lasing

Technical Summary:

Double-clad fiber is consistently used for today’s high-power fiber lasers, which allows the high-power pump light with poor mode quality to be used at the cost of a significant reduction in the pump light’s overlap with the active single-mode core. Consequently, much longer fiber has to be used with reduced peak powers. Further, ytterbium fiber lasers are not typically used as pump lasers, as they usually lase at wavelengths between 1025nm and 1100 nm. The all-solid photonic band fiber feature on this technology, however, enables efficient high-power diffraction limited lasing at ~976 nm. The unique design enables laser light to be launched directly into the active single-mode core, resulting in an increased overlap between the pump light and the active core within the fiber, without increasing core size or fiber length. These novel developments could increase peak powers from fiber lasers by over two orders of magnitude, in conjunction with a two-order reduction in fiber length. This benefit is significant, as the built-in distributed spectral filters are over the entire length of the fiber and are responsible for suppressing transmission in the traditional ytterbium lasing wavelengths. These new capabilities prove for the first time that high-power diffraction-limited pump is not only possible, but also highly efficient.