Multi-MW peak power single-transverse mode operation of a 100 micron core diameter, Yb-doped photonic crystal rod amplifier

We developed a gain-staged master-oscillator/power-amplifier source featuring an Yb-doped, 100&mgr;m-core rod-like photonic crystal fiber (PCF) as the final amplifier. From this PCF, we obtained 1ns pulses of energy in excess of 4.3 mJ, peak/average power ~ 4.5 MW / 42W, and spectral width ~20 GHz. The PCF emitted a near-Gaussian, single-transversemode beam of M2~1.3.