Next generation of tailored mode selective transmission gratings for fiber integrated devices
We report on the selective modal control of tailored femtosecond-written long period fiber gratings (LPFG). It is shown that the excitation of higher order cladding modes is possible with strong selectivity and high precision. The coupling behavior of several gratings dependent on the modified core cross section is determined theoretically and confirmed by experiments. Additional mode field measurements proof our concept. The presented tool could pave the way for a completely new branch of fiber integrated devices such as highly efficient transmission gratings or mode converters.