Patent ID: 8564877

Claim:
A photonic bandgap fiber comprising: a core of a solid material; a first cladding provided around the core; a low-refractive-index region provided in a part of a core vicinity portion of the first cladding and whose average refractive index is lower than that of the core; and a periodic structure region that is arranged in another part of the core vicinity portion of the first cladding which is made of a great many high-refractive-index portions whose refractive index is higher than that of the first cladding arranged in a periodic structure, wherein the core is doped with a rare-earth element, and the first cladding is surrounded by a second cladding of material having a lower refractive index than the first cladding such that the propagation of undesired spontaneously emitted light at a peak-gain wavelength of the rare-earth element, or stimulated Raman scattering, is suppressed, and there are no air holes in the first cladding.