Large mode area all-solid optical fiber lasers with tailored microstructured cladding

Improvements, in terms of output power, spatial beam quality, bend insensitivity are still required in the field of single-mode fiber lasers. A major trend is to increase the active core area to increase the thresholds of nonlinear effects while ensuring a transverse single-mode behavior. Actually, increasing the active ions' concentration is also demanded since it allows a drastic reduction of the fiber length, everything being equal. Two non-exclusive strategies are laid out to overcome fiber laser limitations. On the one hand, a large mode area photonic bandgap fiber is shown to lead to a transverse single-mode fiber laser with very good lasing efficiency. On the other hand, it is demonstrated that surrounding a highly multimode active core by a properly designed microstructured cladding allows the fiber laser to be operated in the single-mode regime.