Large area ion beam sputtered dielectric ultrafast mirrors for petawatt laser beamlines

The latest advances in petawatt laser technology within the ELI Beamlines project have stimulated the development of large surface area dielectrically coated mirrors meeting all demanding requirements for guiding the compressed 30 J, 25 fs HAPLS laser beam at 10 Hz repetition rate and a center wavelength of 810 nm entirely in vacuum. We describe the production and evaluation of Ta₂O₅/HfO₂/SiO₂ ion beam sputtered coated (440 × 290 × 75) mm³ beam transport mirrors. No crazing was observed after thirty vacuum-air cycles. A laser induced damage threshold of 0.76 J/cm² (fluence on mirror surface) was achieved and maintained at high shot rates.