Scattering-initiated parametric noise in optical parametric chirped-pulse amplification

We experimentally study a new kind of parametric noise that is initiated from signal scattering and enhanced through optical parametric amplification. Such scattering-initiated parametric noise behaves similarly to parametric super-fluorescence in the spatial domain, yet is typically much stronger. In the time domain it inherits the chirp of signal pulses and can be well compressed. We demonstrate that scattering-initiated parametric noise has little influence on the pulse contrast but can degrade the energy conversion efficiency substantially.