Dumbbell-shaped Mode-locked Ho³⁺-doped Fiber Laser

Interest in compact and stable sources of ultrashort pulsed radiation in the mid-IR range is due to a number of possible applications, e.g. for spectroscopy, perspective communications, materials processing, biodiagnostics, and etc. One of the promising active medium for such sources are holmium-doped (Ho³⁺) fibers due to their broad gain spectrum of 2-2.2μm. In recent years, Ho³⁺-doped mode-locked fiber lasers have been intensively studied [1] - [3]. However, practically each of the presented laser schemes contains elements that can be damaged by laser radiation (isolators, polarizers, beam splitters, circulators, etc.). For the further use of ultrashort pulsed lasers in complex or hybrid systems as a seed source, the laser scheme should be simplified and free of elements that can fail and affect laser generation. Therefore, it is of interest to study a fiber laser with a simple dumbbell-shaped cavity [4] , [5]. Here, we focused on saturable absorber optimization to obtain a self-starting mode-locked Ho³⁺-doped fiber laser with a dumbbell-shaped cavity.