Long-period fiber grating as wavelength selective element in double-clad Yb-doped fiber-ring lasers

Selection of operating wavelength of the Yb-doped fiber-ring lasers using long-period fiber gratings (LPFGs) is proposed. In the proposed method, customized LPFG that sustains high powers serves as a broad-band rejection filter. It modifies the net gain profile of the laser, enabling the peak gain to occur at a designed wavelength. Spectral range of oscillation between 1050-1110 nm was experimentally demonstrated. The spectral range can be extended to both shorter and longer wavelengths with proper design of the LPFG and length of the Yb-doped fiber. The gratings were inscribed by CO 2 laser and the grating period down to 175 μm was achieved being, to our best knowledge, the shortest reported LPFG period using this technique.