Very-large-mode-area fibers for high-power laser operation

Viac o knihe

In recent decades, ultrashort-pulse laser systems have emerged as essential technologies in both science and industry, with fiber lasers leading the way due to their superior beam quality, high efficiency, and exceptional thermal management, allowing for high average output powers. However, continuous-wave fiber lasers have consistently outpaced pulsed fiber lasers in average-power advancements. This disparity arises because pulsed systems operate at significantly higher intensities within the core, necessitating additional measures to prevent harmful nonlinear effects, such as chirped-pulse amplification, short fiber lengths, and large mode areas. This thesis explores an innovative fiber concept designed for mode-area scaling of high-power, effective single-mode fibers to mode-field diameters exceeding 100 µm. The approach focuses on the delocalization of higher-order modes, with both numerical and experimental investigations into the practical implications for the guiding mechanism, including index matching and thermal gradients. The introduction of large-pitch fibers represents the first examples of this new fiber concept, achieving effective single-mode mode-field diameters beyond 100 µm and setting new records for pulse energy and peak power in ultrashort-pulse fiber-laser systems.