High-performance Yb:CaYAlO₄ dual-crystal regenerative amplifier at 5 and 50 kHz repetition frequency

The Yb:CaYAlO₄ (Yb:CALYO) crystal, which boasts a very broad emission spectrum and moderate thermal conductivity, is highly promising for the generation of high-power femtosecond lasers with short pulse durations. However, research into Yb:CALYO-based high-power femtosecond amplifiers has been limited. Here, we report on a Yb:CALYO-based dual-crystal regenerative amplifier capable of delivering high average power and high pulse energy. The maximum single-pulse energy of 6.5 mJ was achieved at a 5-kHz repetition rate, corresponding to an average power of 32.5 W. Additionally, the maximum average power of 65.2 W was achieved at a 50-kHz repetition rate, corresponding to a single-pulse energy of 1.3 mJ. In both instances, the pulse durations were shorter than 200 fs, accompanied by good power stability. To the best of our knowledge, these results represent the highest average power and pulse energy ever achieved from a Yb:CALYO-based femtosecond amplifier, indicating that Yb:CALYO is an excellent candidate for high-power femtosecond lasers with both high energy and short pulse duration. It is believed that it could develop femtosecond lasers at the 10-mJ level with average power exceeding 100 W and sub-200 fs pulse duration.