Pulse contrast enhancement via non-collinear sum-frequency generation with the signal and idler of an optical parametric amplifier

Abstract

We outline an approach for improving the temporal contrast of a high-intensity laser system by >8 orders of magnitude using noncollinear sum-frequency generation with the signal and idler of an optical parametric amplifier. We demonstrate the effectiveness of this technique by cleaning pulses from a millijoule-level chirped-pulse amplification system to provide >1012 intensity contrast relative to all prepulses and amplified spontaneous emission >5 ps prior to the main pulse. The output maintains percent-level energy stability on the time scales of a typical user experiment at our facility, highlighting the method's reliability and operational efficiency. After temporal cleansing, the pulses are stretched in time before seeding two multipass, Ti:sapphire-based amplifiers. After re-compression, the 1 J, 40 fs (25 terawatt) laser pulses maintain a >1010 intensity contrast >30 ps prior to the main pulse. This technique is both energy-scalable and appropriate for preparing seed pulses for a terawatt- or petawatt-level chirped-pulse amplification laser system.