How can a laser make the most intense ultrashort light pulse? For thirty years, the workhorse of ultrafast optics has been the Ti:Sapphire laser, but such lasers are expensive and cumbersome, and mode locked fiber lasers are a desirable alternative. Even though the gain bandwidth of fiber lasers is not as large as that of solid state lasers, rapid progress in high-power fiber lasers has been made, building on an idea by Piché and Mamyshev, where the laser pulse is alternately subjected to a pair of well-separated spectral filters. In effect forcing the pulse to straddle the gap between the filters, Mamyshev oscillators were shown to generate pulses with less than 20 fs duration and more than 10 MW peak power. The best results have so far been obtained in ring-cavity Mamyshev oscillators. Here, Chen et al. generate high-power ultrashort pulses in the simpler and more compact linear-cavity Mamyshev oscillators. However, the mechanism of the Mamyshev oscillator makes it intrinsically difficult to start, and the Faraday rotators necessary to prevent damage from stimulated Brillouin scattering make it necessary to use a starting protocol where the pump is initially strongly modulated until stable mode locking is achieved. A sophisticated pump control algorithm was implemented electronically, producing a reliably starting linear-cavity oscillator, which, for the first time, can offer performance on par with the bulkier ring-resonator version.

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