STP689: A 1.06µm Laser Absorption Calorimeter for Optical Coatings

    Allen, TH
    Optical Coating Laboratory, Inc., Santa Rosa, California

    Apfel, JH
    Optical Coating Laboratory, Inc., Santa Rosa, California

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

    Pages: 4    Published: Jan 1979


    Abstract

    We describe a laser calorimeter for measuring the absorption of an optical coating deposited on a thin disc. The sample with diameter 2.54cm and thickness between 0.02 to 0.13cm is irradiated with 6 watt CW Nd:YAG laser. The temperature of the coated disc is compared to that of a reference disc using thermistors in mechanical contact with the samples. Measurements are made under vacuum (100 torr) to reduce temperature variations caused by convection. The calorimeter was evaluated by measuring coated and uncoated discs of various thicknesses with absorptances from 9 × 10-6 to 5 × 10-3. These measurements demonstrated a repeatability of ± 2% at an absorptance level of 1 × 10-4 and a sensitivity for a 0.04cm thick substrate of 3.8 × 105 µV/watt. The lower absorption limit of the calorimeter is 2 × 10-6. The results of measurements on polished, uncoated fused silica discs with thicknesses from 0.04 to 0.13cm show a surface absorptance of 6 × 10-6 and a bulk value of 5 × 10-5/cm.

    Keywords:

    Absorption, calorimetry, optical coatings


    Paper ID: STP39100S

    Committee/Subcommittee: F01.02

    DOI: 10.1520/STP39100S


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