The Effect of Macro-bending on Phasing in 6 and 7- Core Large Mode Area Photonic Crystal Fibers

摘要

In this paper, we present the results of a frequency domain analysis of the effect of coiling induced macro-bending on the phasing of the modes of 6 and 7-core large mode area photonic crystal fibers. These fibers may enable fiber laser CW power and pulse energy scaling due to their large effective mode area (～ 4000 square microns), however; phase differences between the cores degrade the output beam quality. We study the effects of bend axis, bend radius, and core geometry on the phasing of the fiber modes. Coiling causes the signals in the individual cores to suffer de-phasing relative to each other in a predictable manner. This allows the possibility of recovering phased output, and thus near diffraction limited beam quality, from amplifiers employing these fibers. Preliminary experimental results are also presented.