Laser peak power scaling and beam quality improvement with a tapered ytterbium rod-type amplifier made by powder sinter technology

At present, the combination of high peak power and near diffraction-limited beam quality is essential for high-power pulsed fiber laser systems combining nanosecond pulses with multi-kilohertz repetition rates. In standard fiber amplifier, parasitic nonlinear effects limit further power scaling due to the small active fiber core. Therefore the scaling to larger effective mode areas (LMA) is a promising solution to suppress nonlinear optical effects and to scale up the peak power [1, 2]. However increasing the fiber core size can severely degrade the fundamental mode operation and beam quality due to the excitation of higher order modes.