Multiple-shot ultraviolet laser damage resistance of nonquarterwave reflector designs for 248 NM

Conference · Fri Jan 01 04:00:00 EST 1982

DOI:https://doi.org/10.1520/STP37260S· OSTI ID:5111471

Newnam, B E; Foltyn, S R; Jolin, L J

The damage resistance of multilayer dielectric reflectors designed for 248 nm has been substantially increased by use of nonquarterwave (QW) thicknesses for the top few layers. These designs minimize the peak standing-wave electric field in the high-index layers, which have proven to be weaker than the low-index components. Previous damage tests of infrared- and visible-wavelength reflectors based on these designs have produced variable results. However, at the ultraviolet wavelength of 248 nm, 99% reflectors of Sc/sub 2/O/sub 3/, MgF/sub 2/, and SiO/sub 2/ strongly demonstrated the merit of non-QW designs. Four sets of reflectors of each of four designs (all QW thickness; one modified-pair substitution; two modified-pair substitution; one modified pair plus an extra half-wave layer of Sc/sub 2/O/sub 3/) were tested for damage resistance with a KrF laser operating at 35 pps with a pulsewidth of 8 ns and spot-size diameter of 0.6 mm. Each of 50 sites were irradiated for 1000 shots or until damage occurred. On the average, the reflectors with one-modified-thickness pair had a 50% higher threshold (10 to 10 sites survived) than the all-quarterwave design. Addition of a second modified-layer pair resulted in no further increase in threshold but the saturation fluence (10 of 10 sites damage) was 110% higher. Reflectors with an additional half-wave of Sc/sub 2/O/sub 3/ had lower thresholds of the order of 10% as expected. The thresholds correlated best with peak-field models, whereas the best model correlating the saturation fluences involved the sum of the upper two scandia layer thicknesses.

• Research Organization: Los Alamos National Lab., NM (USA); Optical Coating Lab., Inc., Santa Rosa, CA (USA)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5111471
• Report Number(s): LA-UR-82-1774; CONF-811117-7; ON: DE82019578
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420300* -- Engineering-- Lasers-- (-1989)
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
COATINGS
DAMAGE
DIELECTRIC MATERIALS
ELECTRIC FIELDS
ELECTROMAGNETIC RADIATION
FABRICATION
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
LASER MIRRORS
LASER RADIATION
LASERS
MAGNESIUM COMPOUNDS
MAGNESIUM FLUORIDES
MATERIALS
MIRRORS
OPTICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RADIATIONS
SCANDIUM COMPOUNDS
SCANDIUM OXIDES
SILICON COMPOUNDS
SILICON OXIDES
SPECTRAL REFLECTANCE
TRANSITION ELEMENT COMPOUNDS
ULTRAVIOLET RADIATION