Sdl Inc.

Jean-Luc Archambault

Stephen G Grubb

Robert G Waarts

Raymond Zanoni

David F Welch

Donald R Scifres

Steven Sanders

Power scaling by multiplexing multiple fiber gain sources with different wavelengths, pulsing or polarization modes of operation is achieved through multiplex combining of the multiple fiber gain sources to provide high power outputs, such as ranging from tens of watts to hundreds of watts, provided on a single mode or multimode fiber.

High power fiber gain media system achieved through power scaling via multiplexing

An optical fiber used as the active amplifying medium in a fiber laser is arranged to have a high insertion loss at an undesired frequency, while retaining a low insertion loss at a desired lasing frequency. In one embodiment, loss at a Raman-shifted frequency is introduced by using an optical fiber which has multiple claddings with an index profile that includes an elevated index region located away from the core, but within the evanescent coupling region of the core. A distributed loss, which can be enhanced by bending, is produced at the Raman frequency which effectively raises the threshold at which Raman scattering occurs in the fiber and therefore results in a frequency-selective fiber. In another embodiment, an absorbing layer is placed around the core region. The absorbing layer is chosen to have a sharp absorption edge so that it absorbs highly at the Raman-shifted wavelength, but minimally at the desired lasing wavelength. In still another embodiment, the optical fiber is constructed with a core with long period gratings formed therein. The gratings are fabricated with a periodicity selected to provide a relatively high insertion loss at the Raman frequency while simultaneously providing a relatively low insertion loss at the lasing frequency. In accordance with yet another embodiment, a bend loss technique is used to suppress amplified spontaneous emission at an unwanted wavelength due to a competing atomic energy level system in a fiber laser.

Optical fiber gain medium with wavelength selective core filter

Optical fiber gain medium with evanescent filtering

A fiber laser uses a chirped Bragg grating as the output coupler and the grating is oriented so that the grating period increases in the direction towards the end of the cavity--the 'red' end of the grating is at the output coupling end of the cavity. This grating orientation unexpectedly produces a relatively large reduction in the noise generated by the fiber laser. In one embodiment, the chirped Bragg grating is produced by transversely doping spaced-apart portions of the longitudinal fiber core with elements that modify the refractive index of the core. The 'chirp' in the grating period is produced by modifying the period of the transversely doped fiber core portions during manufacture of the grating. In another embodiment, a partially reflective chirped fiber grating is used at the input side of the laser as well as at the output side. In yet another embodiment, the chirped grating is manufactured as an unchirped fiber grating where the period of the transversely-doped fiber core portions is constant and a chirp is introduced by selectively bending the fiber along its length, thereby producing a varying grating period.

Noise suppression in cladding pumped fiber lasers

Output power enhancement in optical fiber lasers

Growing community of inventors

Linthicum, MD, United States of America

Jean-Luc Archambault