Patent ID: 8781274

Claim:
A resonator that outputs output light based on excitation light, the resonator comprising: a first optical fiber through which the excitation light and light having the same wavelength as the output light propagate and which is provided with a first reflection element that reflects light having the same wavelength as the output light; a glass rod doped with rare earth elements that are excited by the excitation light to emit light including light having the same wavelength as the output light; a second optical fiber through which light having the same wavelength as at least the output light propagates and which is provided with a second reflection element that reflects the light having the same wavelength as the output light at a lower reflectance than the first reflection element; a first lens that outputs light input from the first optical fiber to the glass rod with an increased diameter and that outputs light input from the glass rod to the first optical fiber with a decreased diameter; and a second lens that outputs light input from the second optical fiber to the glass rod with an increased diameter and that outputs light input from the glass rod to the second optical fiber with a decreased diameter, wherein, inside the glass rod, the excitation light has a larger diameter than the light having the same wavelength as the output light over the entire length of the glass rod.