Multi-Joule Energy Extraction in Diode-Pumped Tm:YLF

We present the first demonstration of a multi-joule diode-pumped Tm:YLF amplifier. The compact demonstrator setup, consisting of a Tm:YLF-based oscillator producing similar to 20mJ, 20ns pulses at 1880nm wavelength that seeds a diode-pumped four-pass Tm:YLF power amplifier, generated pulse energies up to 3.9J with a maximum net gain exceeding 200. No saturation effects were observed within this amplifier, as the output pulse energies increased exponentially with the input pump power. When the amplifier was seeded with the free-running oscillator, with pulse durations still significantly shorter than the 15ms radiative lifetime of Tm:YLF, energies of up to 38J were achieved. To the best of our knowledge, this represents over a 100-fold improvement in the highest reported pulse energy from a Tm:YLF amplifier, and nearly an order of magnitude higher energy than any laser operating near 2 mu m. These results show that Tm:YLF, when operated in an efficient high repetition rate extraction regime and combined with a high-capacity heat removal technique, has the potential to enable a new class of efficient, high peak and average power laser systems to meet the demands of next generation scientific and industrial applications.