Experimental Demonstration of Enhancing Pump Absorption Rate in Cladding-Pumped Ytterbium-Doped Fiber Lasers Using Pump-Coupling Long-Period Fiber Gratings

摘要

A long-period fiber grating (LPFG) was inscribed in a single-mode fiber and was spliced with a ytterbium (Yb)-doped double-clad fiber in order to couple pump radiation of the inner cladding into the core in a cladding-pumped fiber laser. The use of an LPFG permits a partial core-pumping scheme in a cladding-pumping fiber laser because a portion of the pump radiation can be coupled to the core by LPFG. The enhancement of the pump absorption of a Yb-doped cladding-pumped fiber laser as the result of pump coupling by LPFG was 35percent, and the maximal output power increased by up to 55percent when a 20-W pump source is used.