Abstract：An effective method to fabricate two-helix long-period fiber gratings (TH-LFGs) is presented. Based on the coupling mode theory, the conversion of optical vortices (OVs) in TH-LFGs are analyzed in detail. The conversions of OVs with different topological charges: $0\to \pm2$ and $1\to3$ are simulated as three examples and the conversion efficiency higher than 98% can be realized.
Huang H, Milione G, Lavery M P J, Xie G D, Ren Y X, Cao Y W, Ahmed N, Nguyen T A, Nolan D A, Li M J, Tui M, Alfano R R and Willner A E 2015 Sci. Rep.5 14931
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Milione G, Lavery M P J, Huang H, Ren Y, Xie G, Nguyen T A, Karimi E, Marrucci L, Nolan D A, Alfano R R and Willner A E 2015 Opt. Lett.40 1980
Huang H, Xie G D, Yan Y, Ahmed N, Ren Y X, Yue Y, Rogawski D, Willner M J, Erkmen B I, Birnbaum K M, Dolinar S J, Lavery M P J, Padgett M J, Tur M and Willner A E 2014 Opt. Lett.39 197
2016, Vol. 33 
