1 kHz high efficiency Ti:sapphire laser amplifier

We describe a Ti:sapphire multi-pass amplifier with high efficiency at the repetition rate of 1 kHz. In the amplifier, the incident pulse is 0.66 mJ with the pulse duration about 90 ps. The incident pulse is amplified to 7.2 mJ when the pump energy is 23 mJ. The energy efficiency in the amplifier is