Low-dispersion low-loss dielectric gratings for efficient ultrafast laser pulse compression at high average powers

Abstract All-dielectric gratings are ideal for high average power laser pulse compressors due to their low loss and high diffraction efficiencies. However, they have not been utilized in petawatt-class lasers with pulse durations below 100 fs due to a variety of challenges. We present a resonance-free design for low-dispersion (1480 lines/mm) diffraction gratings made of dielectric materials resistant to femtosecond laser damage (SiO 2 /HfO 2 ). A 14 cm diameter sample was fabricated resulting in a mean diffraction efficiency of 99.1% at λ = 810 nm with high spatial uniformity using equipment which can produce gratings up to 1 m diagonal. The implementation of these gratings in the compression of 30 fs pulses in an out-of-plane geometry can result in compressor efficiencies approaching 95%. The measured laser absorption is 500× lower than current ultrafast petawatt-class compressor gratings enabling a substantial increase in average power handling capabilities of these laser systems.