Experimental research on Yb³⁺-doped double-clad photonic crystal fiber lasers

An Yb³⁺-doped double-clad photonic crystal fiber laser was reported. A 5 W maximum output power multimode laser diode with 975 nm central wavelength was used as the pump source, a 6 m long Yb³⁺-doped double-clad photonic crystal fiber was used as gain medium and the F-P cavity is formed by a dichroic mirror and the output face of the fiber. The fiber has a single-mode core with a diameter of 3.9 μm, which has pump absorption of 2300dB/m. The inner cladding has a diameter of 200 μm and is designed with high numerical aperture (0.7 at the pump wavelength). The laser operates under single-mode state at 1.078 μm, the maximum output power is 1.45 W and the slope efficiency is 85.1% with respect to the launched pump power of 1.73 W. The mode competition and self-pulsing effect were regarded as the main factors that affect the output stability performance of the laser.