Damage thresholds and optical stabilities of fluoride HR coatings for 193 nm

We investigated the damage thresholds and optical stabilities of 193 nm fluoride HR coatings consisting of NdF 3 /Na 3 AlF 6 and LaF 3 /Na 3 AlF 3 . These coatings were deposited on fused silica substrates by conventional electron beam (EB) and ion assisted deposition process (IAD). Damage thresholds of LaF 3 /Na 3 AlF 6 HRs were significantly increased by laser conditioning procedure and low index overcoating when they were deposited by EB and low energy IAD process. NdF 3 /Na 3 AlF 6 HRs showed negligible laser conditioning effect except certain few case, and had considerably lower damage thresholds than LaF 3 /Na 3 AlF 6 HRs with conditioning (1.8 J/cm 2 ). Optical stabilities of these HRs were significantly improved by low energy IAD process (50 - 100 eV) which had not harmful influence on damage thresholds.