M. Heck, G. Schwartz, R. G. Krämer, D. Richter, T. A. Goebel, C. Matzdorf, A. Tünnermann, and S. Nolte, "Control of higher-order cladding mode excitation with tailored femtosecond-written long period fiber gratings," Opt. Express 27, 4292 (2019).
We report on the detailed investigation of the core to cladding mode coupling in femtosecond-written long period fiber gratings (LPFG). It is shown that the excitation of higher-order cladding modes with strong selectivity and high precision is possible. The coupling behavior of several gratings, as well as its dependence on the modified core cross-section, is determined theoretically and confirmed experimentally by its spectral response. The presented tool paves the way for a completely new class of tailored LPFGs for different fiber integrated devices.