High efficient Tm3+ doped double cladding silica fiber laser with an intracavity biconical taper

Abstract

A high efficient LD (laser diode) pumped Tm3+ doped double clad silica fiber laser with an intravacity biconical taper was reported. A biconical taper located ∼3 cm from the output end of the fiber laser was fabricated by heating and stretching method with a length 1.5 cm and waist diameter ∼20 µm. The slope efficiency was 49.8% with respected to the launched pump power, and the maximum output power was 1.97 W. Pre and post output laser power ratio was ∼10. This fiber laser was compared with other three biconical tapered fiber lasers (the same fiber with different tapers) and a uniform geometry fiber laser. With intracavity biconical tapers, fiber lasers’ thresholds were ∼1 W higher than the fiber laser without the taper (1.97 W). The pump end’s slope efficiencies of fiber lasers with tapers were 3–5% in contrast with 37.6% of the uniform one. After tapered, the pre and post laser power ratios were much higher than the un-tapered one’s, but not changed much with the launched pump power.