Nanostructured Active Fiber for Mode-Locked and Q-Switched All-Fiber Laser Systems

Mode-locked and Q-switched all-fiber lasers using nanostructured core silica fiber are demonstrated. A novel active fiber has been developed, consisting of a collection of discrete nanorods doped with ytterbium and erbium within an aluminosilicate matrix. The arrangement of nanorods within the fiber core dictates the spatial distribution of amplification and refractive index, enabling the tailored design of the fiber's modal characteristics and dispersion properties. We demonstrate that the employed pumping strategy, which involves stimulating Yb³⁺ ions situated in nanorods and leveraging a non-radiative energy transfer from Yb³⁺ to Er³⁺ ions in distinct nanorods, is effective. This approach facilitates efficient laser performance comparable to fibers with a continuous dispersion of active ions throughout the core. The femtosecond mode-locked pulse at wavelength of 1560 nm, featuring a bandwidth of 5.2 nm, a pulse duration of 860 femtoseconds, and an RF spectral purity with an extinction ratio of 80 dB has been successfully obtained. These results underscore the potential of the nanostructured core fiber concept as an active medium in ultrafast, all-fiber devices