Abstract

Mode instabilities, which have recently been reported in many high-power fiber laser systems, are currently appointed as one of the most limiting factors for power scaling of fiber lasers and amplifiers [1]. They origin from the thermo-optic effect, which causes an increase of the refractive index linearly dependent upon the temperature, which allows propagation of one or more High-Order Modes (HOMs) in an originally single-mode fiber and causes shrinking of the Fundamental Mode (FM) effective area. The impact of this effect scales exponentially with mode field diameter [2], and is therefore very detrimental in ultra-large mode area rod-type Photonic Crystal Fibers (PCFs), whose core diameter can reach up to 100 μm.

© 2013 IEEE