107 mJ Yb : YAG Single Thin-Disk Regenerative Amplifier

Objective In recent years, the thin disk laser has been shown to have significant advantages in terms of structure, efficiency, and beam quality. It has been used to realize ultrafast lasers with high repetition rates, large pulse energies, and high average powers. It has important applications in basic scientific research, industrial production, national defense and military, biomedicine, and other fields. Based on theoretical and numerical analyses, this paper presents an analysis and design of a thin disk regenerative amplifier with a large fundamental mode volume. It can afford a laser output with pulsed energy exceeding 100 mJ. Methods Based on ABCD matrix theory, the optical resonator of the thin disk regenerative amplifier is designed to ensure a laser output with basic mode size. By optimizing the parameters of the pump and seed lasers in the amplifier cavity and managing the thermal effect in the amplification process, the regenerative amplifier can achieve high energy pulse laser output. The experimental device of the disk regeneration amplifier, shown in Fig. 1, contains a seed source, optical isolator, Faraday rotator, Pockels cell, thin film polarizer, regeneration amplifier cavity, and thin disk module with a 48-pass pump structure. Results and Discussions The regenerative amplifier provides a laser output with a repetition rate of 1 kHz, single pulse energy of 107.3 mJ [Fig. 2(a)], pulse width of 1.2 ns [Fig. 2(c)], and optical-to-optical conversion efficiency of 11%. In the experiment, a CMOS camera is used to measure the diameter of the light spot in the x and y directions. The Gauss fitting of the measurement results indicates that the beam quality factor (M-x(2)) of the output laser beam in the x direction and the beam quality factor (M-y(2)) of the output laser beam in the y direction are 1.07 and 1.05, respectively [Fig. 2(b)], and the beam quality is near the diffraction limit. The root-mean-square (RMS) of pulse amplitude stability is 1.26%. The amplified laser spectral width is 2.04 nm [ Fig. 2(d)], which supports the compression of the laser pulse width to 735 fs, as shown by theoretical calculations. Conclusions This paper presents the optimization of the mode matching of the amplifier cavity based on the single thin disk module regenerative amplifier and the realization of the amplification laser output with a single pulse energy of 107 mJ. In future studies, we will continue to optimize the design and experimental scheme of the regenerative amplifier cavity and use multi-layer dielectric gratings to compress the pulse width of a chirped pulse with high pulse energy to achieve laser output with higher pulse energy, higher average power, and narrower pulse width.