Generation of 8 nJ pulses from a normal-dispersion thulium fiber laser
There is great interest in development of better short-pulse lasers in the 2-5 μm region. We show the first thulium-doped fiber laser at 2 μm to reap the performance benefits of pulse propagation at normal dispersion. Ultra-high numerical-aperture fibers provide normal dispersion and are employed to shift the cavity dispersion to the normal regime. A laser that exhibits elements of self-similar pulse evolution generates 8-nJ and 130-fs pulses, which corresponds to 4 times the highest peak power achieved previously by a Tm fiber laser.