High-power fiber laser based on a non filamented-core fully-aperiodic large pitch fiber

Since the double-clad fiber architectures development, fiber-based lasers have witnessed an impressive power scaling [1]. The rise of the extracted signal power has been accompanied by the development of Very Large Mode Area (VLMA) fiber designs allowing the overtake of some key hurdles like the non-linear process or photo-darkening [2]. However, due to a significant deposition of heat along and across the section of VLMA fibers, a new phenomenon, referring to as thermal-induced modal instabilities, has been evidenced recently as being the current limitation that hampers any further power increase in the field of high beam quality fiber lasers [3]. Much of a work has been done by researchers so as to clarify the origin of such detriment, leading to the evidencing of a thermal-induced long-period gratings that enable for an effective coupling of the fundamental mode with an unwanted high-order core mode (typically the LP11) [4].