Compact aberration free multi loop stretcher for OPCPA system

A compact aberration free multi loop stretcher system for OPCPA with pulse confining structure was demonstrated, where the six-loop pulse was observed. To compensate for the energy loss, a high gain optical parametric amplification (OPA) was used. The conversion efficiency of the OPA is strongly affected by the pulse width ratio between the signal pulse and pump pulse and efficient amplification with pump depletion was observed.