Leakage channel fibers with microstuctured cladding elements: a unique LMA platform.

We present a novel design of leakage channel fiber (LCF) that incorporates an air-hole lattice to define the modal filtering characteristics. The approach has the potential to offer single-mode, large mode area (LMA) fibers in a single-material platform with bend loss characteristics comparable to all-solid (LCFs) whilst at the same time providing significant fabrication benefits. We compare the performance of the proposed fiber with that of rod-type photonic crystal fibers (PCFs) and all-solid LCFs offering a similar effective mode area of ~1600μm(2) at 1.05μm. Our calculations show that the proposed fiber concept succeeds in combining the advantages of the use of small air holes and the larger design space of rod-type PCFs with the improved bend tolerance and greater higher order mode discrimination of all-solid LCFs, while alleviating their respective issues of rigidity and restricted material design space. We report the fabrication and experimental characterization of a first exemplar fiber, which we demonstrate offers a single-mode output with a fundamental mode area ~1440µm(2) at 1.06µm, and that can be bent down to a radius of 20cm with a bend loss of <3dB/turn. Finally we show that the proposed design concept can be adopted to achieve larger mode areas (> 3000µm(2)), albeit at the expense of reduced bend tolerance.