Article Abstracts | July 2007
The complete article appears in the July 2007 issue of Photonics Spectra. If you do not have a copy of this issue,
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Lasing in a Gain-Guided, Index-Antiguided Fiber
This new approach may provide a path to efficient, single-mode, multikilowatt fiber lasers.
by Dr. Michael Bass and Dr. Martin C. Richardson, CREOL
In the past decade and a half, fiber lasers with very high multimode output powers have been developed by doping the core of such fibers with ions that can lase. These fiber lasers are pumped by light from diode-laser arrays that is coupled into both the core and the cladding, exciting ions over the entire length of the fiber.
An inherent problem with these powerful lasers is that they cannot readily be made to oscillate in a single transverse mode, so the beam quality is not suitable for some applications. Single-mode oscillation requires a small core, typically 8 to 10 μm in diameter. Larger cores allow high-order modes to oscillate. But the small core leads to high intensities, and high intensities propagating over long distances lead to deleterious nonlinear effects such as stimulated Raman and Brillouin scattering. Many researchers have proposed clever ways of avoiding the nonlinearities, but not one of these to date has provided the robustness and reliability suitable for all applications.
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