Research on Picosecond Laser Regenerative Amplifier Based on Thin-Disk Gain Medium

In recent years, ultrafast lasers have become the main source of laser precision manufacturing. The further improvement of laser processing efficiency and capability requires ultrashort pulse lasers with higher average power and single pulse energy. In this paper, two picosecond thin-disk laser regenerative amplifiers are developed based on one thin-disk module and two thin-disk modules connected in series, respectively. For the regenerative amplifier with one thin-disk module, on the basis of a seed source with a pulse width lower than 10 ps, the pulse laser with an average power of 44.2 W, a pulse width of 9.3 ps, and single pulse energy of 220 mu J is output, and the optical-optical efficiency of the amplifier is about 13.4 %. For the regenerative amplifier based on two thin-disk modules connected in series, a seed source with a pulse width of 800 ps is adopted; then, we obtain a laser output of 126 W at a repetition frequency of 200 kHz and maximum single pulse energy of 0.96 mJ at a repetition frequency of 100 kHz. Considering the effect of amplified spontaneous emission, the dynamic process of the regenerative amplifier with one thin-disk module is theoretically modeled, and the results are consistent with the experimental ones. Further simulations show that the low single-pass gain makes the optical-optical efficiency of the thin-disk regenerative amplifiers greatly affected by the intra-cavity loss, and reducing the intra-cavity loss is one of the keys to achieving a high-efficiency thin-disk regenerative amplifier.