Patent ID: 8270442
Filing Date: 2012-09-18
Classification: G02B,H01S

Abstract:
1. An optical fiber laser comprising: a master oscillator which is a laser oscillator producing a seed beam; and a power amplifier which is an optical amplifier connected to a subsequent stage of the master oscillator and amplifying the seed beam emitted from the master oscillator and outputting a laser beam, wherein the power amplifier comprises: a plurality of excitation light sources; excitation ports each of which is connected to the excitation light sources and which an excitation light emitted from each of the excitation light source enters; a signal port which a laser beam emitted from the master oscillator enters; an optical coupler with an exit port that outputs the excitation lights from the excitation ports together with the laser beam from the signal port; and an optical fiber connected to the exit port, wherein the optical fiber is a photonic bandgap fiber, and wherein the optical fiber has a loss wavelength characteristic in that a photonic bandgap region is narrower than a gain wavelength band in a graph with an axis of abscissa representing a wavelength and an axis of ordinate representing a loss amount, wherein the optical fiber comprises: a region; a core portion made of a solid material doped with a rare-earth element, provided in the region, and having a higher refractive index than the region; a first cladding provided around the region; and a periodic structure portion in which a multitude of high refractive index portions with a refractive index higher than that of the first cladding are arranged in a periodic structure, the periodic structure portion being provided in a vicinity of the region in the first cladding.