| 摘要 |
A tapered fiber laser having a multi-mode section, a single-mode section, and either a tapered section or fundamental mode matching junction therebetween. The multi-mode section has a large core to directly receive pump light from a broad stripe laser or diode bar, and a length preferably longer than the absorption length of the pump light (so optical amplification occurs predominantly in the multi-mode section). Doping levels can be increased to reduce the multi-mode length. The taper angle is sufficiently small to produce adiabatic compression of the fundamental mode from the multi-mode to single-mode sections, and acts as a cutoff filter favoring lasing of the fundamental mode within the multi-mode section. Alternately, the step junction may have a mode field diameter matched to the lowest-order mode, with laser light output via the single-mode section. The invention can be applied to waveguides (particularly those having an aspect ratio corresponding to a broad stripe laser source), doped with ytterbium or neodymium ions, and is particularly advantageous as a pump source for an erbium-doped fiber amplifier (EDFA).
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