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Proceedings Paper

Design of refractive-index and rare-earth-dopant distributions for large-mode-area fibers used in coiled high-power amplifiers
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Paper Abstract

We have numerically compared the performance of various designs for the core refractive-index (RI) and rare-earth-dopant distributions of large-mode-area fibers for use in bend-loss-filtered, high-power amplifiers. We first established quantitative targets for the key parameters that determine fiber-amplifier performance, including effective LP01 modal area (Aeff, both straight and coiled), bend sensitivity (for handling and packaging), high-order mode discrimination, mode-field displacement upon coiling, and index contrast (manufacturability). We compared design families based on various power-law and hybrid profiles for the RI and evaluated confined rare-earth doping for hybrid profiles. Step-index fibers with straight-fiber Aeff values > 1000 &mgr;m2 exhibit large decreases in Aeff and transverse mode-field displacements upon coiling, in agreement with recent calculations of Hadley et al. [Proc. of SPIE, Vol. 6102, 61021S (2006)] and Fini [Opt. Exp. 14, 69 (2006)]. Triangular-profile fibers substantially mitigate these effects, but suffer from excessive bend sensitivity at Aeff values of interest. Square-law (parabolic) profile fibers are free of modal distortion but are hampered by high bend sensitivity (although to a lesser degree than triangular profiles) and exhibit the largest mode displacements. We find that hybrid (combined power-law) profiles provide some decoupling of these tradeoffs and allow all design goals to be achieved simultaneously. We present optimized fiber designs based on this analysis.

Paper Details

Date Published: 22 February 2007
PDF: 11 pages
Proc. SPIE 6453, Fiber Lasers IV: Technology, Systems, and Applications, 64531C (22 February 2007); doi: 10.1117/12.701594
Show Author Affiliations
Roger Lee Farrow, Sandia National Labs. Livermore (United States)
G. Ronald Hadley, Sandia National Labs. Albuquerque (United States)
Dahv A. V. Kliner, Sandia National Labs. Livermore (United States)
Jeffrey P. Koplow, Sandia National Labs. Livermore (United States)

Published in SPIE Proceedings Vol. 6453:
Fiber Lasers IV: Technology, Systems, and Applications
Donald J. Harter; Andreas Tünnermann; Jes Broeng; Clifford Headley, Editor(s)

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