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Master Oscillator Fiber Amplifier

Acronym: MOFA or MOPFA

Definition: a laser system containing a fiber amplifier for boosting the output power

Categories: fiber optics and waveguides, lasers, optical amplifiers

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The term master oscillator fiber amplifier (MOFA, MOPFA, or fiber MOPA) is a variation of the term master oscillator power amplifier (MOPA), meaning a system where the power amplifier is a fiber amplifier. The latter is usually a cladding-pumped high-power amplifier, often based on an ytterbium-doped fiber. The main attractions of such fiber-based power amplifiers are:

master oscillator fiber amplifier (fiber MOPA)
Figure 1: Setup of a single-stage core-pumped fiber MOPA. For higher power levels, a second amplifier stage with double-clad fiber may be added. The seed laser diode may be operated in a pulsed regime.

However, the use of fibers also has disadvantages:

It can be attractive to use a gain-switched laser diode as seed laser for a fiber MOPA. Such devices compete with Q-switched lasers, e.g. for application in laser marking. Their advantages partly lie in their flexibility concerning output formats: it is easy to modify not only the pulse repetition rate but also the pulse duration and shape, and of the course the pulse energy.

A special aspect of MOFAs is that the saturation power even of a large mode area double-clad fiber is low compared with the typical output power. Therefore, the power extraction can be as efficient as in a fiber laser, even for relatively low seed powers.

See also: master oscillator power amplifier, optical amplifiers, fiber amplifiers, high-power fiber lasers and amplifiers, Spotlight article 2008-09-24, Spotlight article 2008-12-16
and other articles in the categories fiber optics and waveguides, lasers, optical amplifiers

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