10-mJ-class dual-crystal Yb:KGW regenerative amplifier with M-shaped spectrum for seeding Yb:YAG lasers

We present a high-energy broadband regenerative amplifier (RA) at a repetition rate of 1 kHz with an M-shaped spectral profile, realized by incorporating two orthogonally oriented Ng-cut Yb:KGW within a single RA. Benefiting from a large-mode cavity configuration, the high-damage-threshold optical components, a thermally insensitive cavity design, and a quasi-continuous-wave (QCW) pumping scheme, the amplifier delivers output pulse energies of 13.8 mJ and 12.9 mJ before and after spectral shaping, respectively. To the best of our knowledge, this represents the highest pulse energy reported to date for a Yb:KGW RA operating at room temperature and 1 kHz. The amplifier exhibits an M-shaped spectrum with a spectral dip centered at 1030 nm, together with excellent beam quality and energy stability, making it a promising front end for Yb:YAG amplifier systems targeting the generation of hundred-millijoule, ~200-fs pulses.