Multi Trench Fiber: an ultra large mode area solution for industrial manufacturing

Jain, D., Baskiotis, C. and Sahu, J.K. (2014) Multi Trench Fiber: an ultra large mode area solution for industrial manufacturing. 2nd Annual EPSRC Manufacturing the Future Conference, Cranfield, United Kingdom. 17 - 18 Sep 2014.

Abstract

High power fiber lasers with good beam quality have shown their potential for numerous applications in material processing, defense, medicine, and space communications etc. Fiber lasers up to 10kW with single mode output have been demonstrated [1]. However, further scaling of power level requires proper management of non-linear effects (like Stimulated Raman Scattering, Stimulated Brillouin Scattering etc). One approach to mitigate non-linear effects is to increase the effective area (Aeff) of the fundamental mode. However, increasing the Aeff of the fundamental mode by increasing the core size, leads to propagation of higher order modes in a conventional fiber, which in, turn deteriorates the beam quality. In the recent years, several fiber designs having large mode area while ensuring single mode operation have been proposed, like Photonic Crystal Fibers (PCFs) [2] and 2-D all solid Photonic Band Gap Fibers (2D-ASPBGFs) [3]. These fibers have shown potential for high power fiber lasers but their fabrication involve stack and draw process, which is quite time consuming and expensive, making them unsuitable for large scale industrial manufacturability. Recently, we proposed the Multi Trench Fibers (MTFs) for high power fiber laser applications [4]. These are cylindrical symmetrical structures, which can be easily manufactured by a conventional fiber fabrication technique, like Modified Chemical Vapor Deposition (MCVD). Fig. 1 (a) shows the schematic of the proposed MTF. Fig. 1(b) shows the cross sectional image of the MTF fabricated using the MCVD process. MTF offers single-mode operation by offering higher losses to the higher order modes, through resonant coupling to the ring modes. Numerical simulation shows the potential of achieving ultra large Aeff 12,000m2 for a 140 m core with good beam quality (M2<1.2), for MTF in rod type configuration, which cannot be bent. Moreover, MTF can offer Aeff larger than 700m2 at a bend radius of 20cm.

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Contributors

Author: J.K. Sahu

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