High-power ultrafast lasers are widely used in advanced manufacturing, information, microelectronics, biomedicine, national defense and military fields, and related scientific research is crucial for promoting national scientific and technological innovation and high-quality development. Thin-section laser systems are widely used in advanced manufacturing, information, microelectronics, biomedical, defense and military fields...
High-power ultrafast lasers are widely used in advanced manufacturing, information, microelectronics, biomedical, national defense and military fields, etc. The related scientific research is crucial to promote national scientific and technological innovation and high-quality development. By virtue of its high average power, large pulse energy and excellent beam quality, thin-film laser system has a great demand in scientific and industrial fields such as attosecond physics and material processing, and has received extensive attention from countries all over the world. However, at present, there are still deficiencies in key technologies such as thin-film gain device preparation, cooling system design and packaging, and multi-stroke pumping system, which seriously limit the further development of high-power ultrafast thin-film lasers in China.
Funded by the National Key Research and Development Program of China (No.2022YFB3605800), the team of Prof. Shuangchen Ruan and Associate Prof. Xing Liu from Shenzhen University of Technology (SZUT) has recently achieved a high-performance (high-stability, high-power, high-beam-quality, and high-efficiency) ultra-fast thin-film laser output by adopting self-developed thin-film module and regenerative amplification technology. By designing the regenerative amplification cavity and controlling the surface temperature and mechanical stability of the disk crystal inside the cavity, a laser output with a single pulse energy >300 μJ, pulse width <7 ps, and an average power >150 W was realized, with a maximum optical-to-optical conversion efficiency of 61%, which is also the highest optical-to-optical conversion efficiency reported to date by regenerative amplification of ultra-fast thin-film, and a beam quality factor of M2<1.06@150W, 8h stability RMS, and a beam quality factor of M2<1.06@150W. 150W, 8h stability RMS<0.33%, which marks an important progress in high-performance ultrafast thin-film lasers, which will provide more possibilities for high-power ultrafast laser applications.
The results were published in High Power Laser Science and Engineering, Vol. 2, No. 2, 2024 (Sizhi Xu, Yubo Gao, Xing Liu, Yewang Chen, Deqin Ouyang, Junqing Zhao, Minqiu Liu, Xu Wu, Chunyu Guo, Cangtang Wu, and Yewang Chen). Chunyu Guo, Cangtao Zhou, Qitao Lue, Shuangchen Ruan. High-repetition-rate and high-power efficient picosecond thin-disk regenerative amplifier[J ]. High Power Laser Science and Engineering, 2024, 12(2): 02000e14).
High heavy frequency and high power thin-disk regenerative amplifier system
Fig. 1 Thin-flake regenerative amplification system
The structure of the thin-flake laser amplifier is shown in Fig. 1. It includes a fiber seed source, a thin-film laser head and a regenerative amplification cavity. The seed source is an ytterbium-doped fiber oscillator with an average power of 15 mW, a central wavelength of 1030 nm, a pulse width of 7.1 ps and a repetition frequency of 30 MHz. The thin-film laser head uses a homemade Yb: YAG crystal with a diameter of 8.8 mm and a thickness of 150 µm and a 48-stroke pumping system. The pump source uses a 969 nm wavelength-locked zero-phonon line LD, which reduces the quantum defect to 5.8%. A unique heat dissipation structure effectively cools the lamellar crystal and ensures the stability of the regeneration cavity. The regenerative amplification cavity consists of Pockels Cell (PC), Thin Film Polarizers (TFP), Quarter-Wave Plates (QWP), and a highly stable resonant cavity. An isolator (Isolator) is used to prevent the amplified light from reversing and damaging the seed source.The Isolator structure consisting of TFP1, Rotator and Half-Wave Plates (HWP) is used to isolate the input seed from the amplified pulse. The seed pulse enters the regenerative amplification chamber through TFP2. A barium bias borate (BBO) crystal, PC, and QWP combine to form an optical switch, and a periodic high voltage is applied to the PC to selectively capture the seed pulse to propagate it back and forth through the cavity. The desired pulse is oscillated in the cavity by fine tuning of the Pukel box voltage application period for effective amplification during round-trip propagation.
Fig. 2 Output performance of the regenerative amplifier system for thin-film
At 1 MHz, the regenerative amplifier has a maximum output power of 154.1 W, an optical-to-optical conversion efficiency of up to 61%, a beam quality factor of MX2 = 1.05 and MY2 = 1.06 at the highest power, and an 8-hour power stability of RMS < 0.33%.
