Patent ID: 7769058

Claim:
An optical fiber laser for oscillating a laser light by introducing an excitation light for exciting a rare earth element, comprising: an optical fiber doped partially by the rare earth element and wrapped around a base member, the base member having an outer surface that includes a flat surface portion and a curved surface portion, one part of an outer circumferential area of said wrapped optical fiber being processed in order to form a flat surface over the flat surface portion of the base member, wherein the flat surface of the optical fiber and the flat surface portion of the base member are arranged in parallel to each other, and wherein the base member has an oval tubular shape and an oval cross section, and a mirror surface is formed at an outer circumferential area of the base member; and a prism, whose one face is made contacted to the flat surface of the outer circumferential area of the optical fiber, wherein one face of the prism is contacted to one face of the flat surface, leaving an exposed flat surface of the wrapped optical fiber, the exposed flat surface not contacting the prism, wherein a metal film for reflecting the excitation light is coated in contact with the prism and in contact with the exposed flat surface not contacting the prism, and wherein the excitation light is introduced into said optical fiber through a surface of said prism other than said one face of said prism.