With the continuous advancement of fundamental scientific research and industrial technologies, there is a growing demand for ultrafast lasers with high repetition rates (≥1 kHz) and large pulse energies (≥10 mJ). This report presents a femtosecond regenerative amplifier system based on a 100 K cryogenically cooled Yb:CaF₂ crystal as the gain medium, with a focus on investigating the period-doubling effect during amplification and thermal lens compensation in the regenerative cavity. Under an absorbed pump power of 63.4 W, the system achieved stable regenerative amplification with an output energy of 10.3 mJ at 1 kHz, corresponding to an average slope efficiency of 24.7%. The beam quality exhibited an M² factor of less than 1.2, and the spectral bandwidth reached 4.37 nm. After compression using a grating compressor, a pulse duration of 283 fs was obtained, approaching the Fourier-transform limit.

Regenerative amplification,Yb-doped solid-state laser,Chirped pulse amplification,Period-doubling effect,Ultrafast laser