Ultra high numerical aperture high power optical fiber laser

Abstract

An optical fiber structure includes: an optical fiber comprising a rare earth doped core (that may be single mode or multi-mode), or several single mode cores, surrounded by a silica material; a glass cylinder tube containing the optical fiber along a length thereof such that the doped core is located at a center of the glass cylinder for a single core, or arranged geometrically around the center for multiple cores; and a support structure disposed between the light guiding section of the optical fiber optical fiber and an inner wall of the tube that functions as a portion of the support structure of the light guiding portion of the optical fiber. The support structure is arranged such that the effective cladding of the core is a gas contained between the optical fiber and the inner wall of the tube for providing the optical fiber with a numerical aperture that is approximately one. A polarization maintaining embodiment is described, as are methods for fabricating the optical fiber structures. To reduce the overall length of the fiber, a chirped Bragg grating may be written into a multi-mode section of the fiber. The optical fiber structures can be used as gain elements in optical fiber lasers, such as those having applications in communications, medical, and manufacturing environments.