We have demonstrated a pulsed 1064 nm PM Yb:fiber laser system incorporating a seed source with a tunable pulse repetition rate and pulse duration and a multistage fiber amplifier, ending in a large core (>650 μm2 mode field area), tapered fiber amplifier. The amplifier chain is all-fiber, with the exception of the final amplifier’s pump combiner, allowing robust, compact packaging. The air-cooled laser system is rated for >60 W of average power and beam quality of M2 < 1.3 at repetition rates below 100 kHz to 10’s of MHz, with pulses discretely tunable over a range spanning 50 ps to greater than 1.5 ns. Maximum pulse energies, limited by the onset of self phase modulation and stimulated Raman scattering, are greater than 12.5 μJ at 50 ps and 375 μJ at 1.5 ns , corresponding to >250 kW peak power across the pulse tuning range. We present frequency conversion to 532 nm with efficiency greater than 70% and conversion to UV via frequency tripling, with initial feasibility experiments showing >30% UV conversion efficiency. Application results of the laser in scribing, thin film removal and micro-machining will be discussed.
Gain-guided and index anti-guided waveguides hold great promise to increase laser output power while maintaining single mode operation. Although lasing in GG-IAG fibers was demonstrated, slope efficiency is poor and output power is low. This work presents the first, to the best of our knowledge, lasing characteristics of a diode-pumped GG-IAG planar waveguide in a plano-plano resonator configuration. The laser waveguide is fabricated using 1% doped Nd:YAG core with diffusion bonded TGG claddings. With continuous-wave pumping, 8.5% slope efficiency is demonstrated and an output power of 1.5W achieved, the highest power reported so far from a GG-IAG waveguide laser. Under such pumping condition, however, thermal lensing is shown to override gain guiding and mode narrowing is observed.