Multipass stretcher for chirped-pulse amplification

We reported an active multipass stretcher which can deliver chirped pulse with high energy, adjustable duration and high beam quality. The stretcher system is based on a Martinez stretcher and a regenerative amplifier. The stretched pulse duration can be adjusted without changing the layout. With 1 ns stretched pulse output per roundtrip, chirped pulse with more than 10 ns can be obtained after several round-trips. A laser amplifier is introduced into the cavity to compensate the energy loss caused by the diffraction efficiency of gratings, and several millijoules pulse energy can be obtained after stretching and amplification. Benefit with the advantage of the regenerative structure, the stretched pulses have an excellent beam quality with M2 of 1.1. This novel stretcher is significant for high peak power laser systems.