Patent ID: 8705912

Claim:
A light source apparatus comprising: a first light source unit that outputs single-mode light with a main output wavelength λ 1 ; an amplifier configured to amplify output light from light source; and a delivery optical fiber into which the output light from the first light source unit is inputted, after the output light is amplified, wherein the delivery optical fiber has a photonic bandgap structure in a core-surrounding portion located around a core thereof, the delivery optical fiber having, in the core, a first wavelength band having a first loss value that is substantially constant throughout the first wavelength band and a second wavelength band having a second loss value higher than the first loss value in the first wavelength band, as power transfer loss characteristics according to change in a longitudinal direction of an output light propagating region in a fiber cross section, wherein the wavelength λ 1 exists in the second wavelength band, and wherein a bending state of the delivery optical fiber is set so that the light with the wavelength λ 1 outputted from the delivery optical fiber becomes a ring-shaped light intensity distribution in the core-surrounding portion.