SEDL / STP / STP954-EB / STP23135S

Angular Dependence of Multilayer-Reflector Damage Thresholds

Newnam, BE
Los Alamos National Laboratory, Los Alamos, New Mexico

Foltyn, SR
Los Alamos National Laboratory, Los Alamos, New Mexico

Gill, DH
Los Alamos National Laboratory, Los Alamos, New Mexico

Jolin, LJ
Los Alamos National Laboratory, Los Alamos, New Mexico

Pages: 10    Published: Jan 1986

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Abstract

The damage resistance of HfO²/SiO² multilayer dielectric reflectors was measured as a function of angle of incidence with 351-nm XeF-laser irradiation. The laser produced nominal 10-ns pulses at a repetition rate of 35 pps. A series of reflectors designed for 0°, 30°, 45°, 60°, 75°, and 85° was tested with an S-plane polarized beam. To account for variations in the separate coating depositions, some of the coating designs were tested at two angles of incidence. At large angles of incidence, we did not observe the anticipated large increases in damage threshold predicted theoretically on the basis of spatial dilution (1/cosθ) of the intensity at the reflector surface and standing-wave electric fields. For example, the threshold for a reflector designed and tested at 85° was only a factor of 2.5 larger than that of normal-incidence reflectors tested at 0°. Several possible mechanisms to explain this discrepancy were considered.