PHOTONIC BAND GAP FIBER, AND FIBER LASER DEVICE USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a photonic band gap fiber capable of propagating light having large power while removing the light in a higher order mode and propagating the light in a basic mode, and also to provide a fiber laser device using the same.SOLUTION: Disclosed is a photonic band gap fiber which is used in a state where at least a part is bent in a length of 15 cm or more and 25 cm or less. Numerous high refractive index parts 57 are 19 cell core type and arranged in three layers, and a V value is 1.5 or more and 1.63 or less. The high refractive index part 57 has conditions determined that the relative refractive index difference is &Dgr;% and the grating constant is Λμm so that a higher order mode is removed in a portion bent in such a manner.