Dual Band Active Nanostructured Core Fiber for Two-Color Fiber Laser Operation

We present the experimental verification of a new type of an active nanostructured fiber devoted to simultaneous laser emission at two wavelengths: 1040 nm and 1534 nm in the fundamental mode. The fiber core is formed with two types of nanorods made of a phosphate glass doped with either Yb 3+ or co-doped with Yb 3+ /Er 3+ ions, respectively. A distribution of the nanorods in the core allows to control relative gain and modal properties of the fiber at both wavelengths and to maintain the single mode performance with a high quality beam generated in a single fiber core. The double-cladding fiber structure allows efficient excitation with a single 975 nm diode pump laser. As a proof-of-concept we demonstrated an active fiber with 15 µm core diameter composed of 6649 nanorods with an individual diameter of 160 nm. The fiber was used in a laser setup. The laser operation was verified for simultaneous two-color laser generation at output power levels of 0.78 W and 0.42 W with slope efficiency of 23.0% and 9.8% at 1040 nm and 1534 nm, respectively.