Fiber laser

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A fiber laser or fibre laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, and thulium. Semiconductor laser diodes are commonly used for pumping fiber lasers. Fiber lasers can have extremely long gain regions. They can support very high output powers because the fiber's high surface area to volume ratio allows efficient cooling, and its waveguiding properties reduce thermal distortion of the beam. Fiber lasers are also typically much smaller than rod or gas lasers of comparable power, as the fiber can be coiled, so that a couple of meters of gain medium can be fitted into a much smaller space.

Many fiber lasers are based on double-clad fiber. The gain medium forms the core of the fiber, which is surrounded by two layers of cladding. The lasing mode propagates in the core, while a multimode pump beam propagates in the inner cladding layer. The outer cladding keeps this pump light confined. This arrangement allows the core to be pumped with a much higher power beam than could otherwise be made to propagate in it, and allows the conversion of pump light with relatively low brightness into a much higher-brightness signal. As a result, fiber lasers and amplifiers are occasionally referred to as "brightness converters."

Applications include: telecommunications, networking, spectroscopy, and medicine.