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When working with ultrashort pulse fiber amplifiers, unwanted effects like self-phase modulation or optically induced damage can already occur at low peak intensities and, thus, at low pulse energies due to the confinement of the light in small signal cores. To mitigate these effects, spectrally dispersive elements are used to stretch the pulses prior amplification and recompress them afterwards. This method is called chirped-pulse amplification (CPA). The dispersion can be achieved with different elements such as optical gratings or prisms. With this architecture, femtosecond pulses can be stretched up to the nanosecond regime, thus allowing us to build ultrashort-pulse fiber lasers with the highest peak powers to date [1].
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