Optimal inner cladding shapes for double-clad fiber lasers

Summary form only given. Double-clad fiber lasers typically consist of a doped single-mode core carrying and amplifying a laser signal in the 10-W cw range, a large (100-400 /spl mu/m) inner cladding carrying the pump radiation and confining the signal, and an outer cladding confining the pump radiation. Due to the small area ratio the coupling of the pump radiation from the inner cladding to the core is relatively weak. Achieving high laser efficiency depends on optimizing this coupling, which in turn depends on the cross-sectional shape of the inner cladding. We have determined the optimizing condition for this cladding shape.