High-power air-clad large-mode-area photonic crystal fiber laser

In this paper, we present the results of a high power photonic crystal fiber laser, where the well-known concepts of double-clad and large-mode-area design are transfered to an actively doped microstructured fiber. The double-clad design is achieved by surrounding the inner cladding (pump core) with a web of silica bridges (as thin as 390 nm and approximately 50 μm long) which are substantially narrower than the wavelength of the guided radiation. It is concluded that air-clad microstructure ytterbium-doped large-mode-area fibers should be scalable to kW-level output powers, where nonlinearity will limit the performance.