Effect of Overcoats on 355-nm Reflectors

    Published: Jan 1986

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    Previous experiments have demonstrated that halfwave overcoats of a low-index coating material are effective in increasing the damage thresholds of dielectric high reflector coatings (HR's) at the wavelengths of 1064 nm and 248 nm. This overcoat layer led to a 50% increase in damage threshold at 1064 nm and to a 100% increase in threshold at 248 nm. This paper presents new results on the effect of halfwave overcoats at an intermediate wavelength: 355 nm.

    Results reported at last year's Boulder Damage Symposium indicated that halfwave silica overcoats were detrimental to the damage thresholds of HR's at 355 nm. New results confirm that silica overcoats decrease thresholds and also show that magnesium fluoride overcoats do not improve the thresholds at 355 nm. A series of eight reflectors without overcoats had an average threshold of 2.4 J/sq. cm. The addition of silica overcoats decreased the average threshold by 2%, while magnesium fluoride overcoats decreased the threshold by an average of 7%.


    electric field, high energy laser, laser damage, laser reflector, overcoat, reflector, thin film

    Author Information:

    Carniglia, CK
    Optical Coating Laboratory, Inc., Santa Rosa, CA

    Hart, TT
    Optical Coating Laboratory, Inc., Santa Rosa, CA

    Staggs, MC
    Optical Coating Laboratory, Inc., Santa Rosa, CA

    Committee/Subcommittee: E13.01

    DOI: 10.1520/STP23129S

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