Demonstration of 85%pump depletion and 10-6 noise content in quasi-parametric chirped-pulse amplification

Full pump depletion corresponds to the upper limit of the generated signal photons relative to the pump pulse;this allows the highest peak power to be produced in a unit area of ultraintense laser amplifiers.In practical systems based on optical parametric chirped-pulse amplification,however,the typical pump depletion is only~35%.Here,we report quasi-parametric chirped-pulse amplification(QPCPA)with a specially designed 8-cm-thick Sm∶YCOB crystal that highly dissipates the idler and hence improves pump depletion.We demonstrate 56%QPCPA energy efficiency for an 810-nm signal converted from a 532-nm pump,or equivalently 85%pump depletion.As another advantage,such a record high depletion greatly suppresses the parametric superfluorescence noise in QPCPA to only~1.5×10-6 relative to the amplified signal energy.These results pave the way to beyond the ten-petawatt peak power of the currently most intense lasers.