This study develops a Yb:KGW dual-crystal based regenerative amplifier. The thermal lensing and gain narrowing effects are compensated by the dual-crystal configuration. Sub-nanojoule pulses are amplified to 1.5 mJ with 9 nm spectral bandwidth and 1 kHz repetition rate using the chirped pulse amplification technology. Consequently, 1.2 mJ pulses with a pulse duration of 227 fs are obtained after compression. Thanks to the cavity design, the output laser was near the diffraction limited beam with M2 around 1.1. The amplifier has the potential to boost energy above 2 mJ after compression and acts as a proper front end for the future kilohertz Terawatt-class diode-pumped Yb:KGW laser system.
