25 September 2008 Characterization of high reflecting coatings and optical materials by direct absorption and cavity ring down measurements
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Abstract
At 193nm and 527 nm, the laser induced deflection (LID) technique is applied to measure directly and quantitatively residual absorptions in high reflecting optical coatings. In addition, combined measurements of absorption, transmission, reflectivity and scattering for HR mirrors at 193 nm reveal very good results for the energy balance. Cavity ring down (CRD) spectroscopy is a sensitive technique to characterize highest mirror reflectivities by determine the photon lifetime within a resonator. A CRD setup, designed for both, cw and pulsed lasers, serves for measurements. First measurements at λ = 532 nm reveal ultra high reflectivities of r ≥ 99.99 %. Accompanying, residual absorption of HR coatings (ppm range) is measured directly by LID technique to quantify the different loss mechanisms contributing to the CRD result. Additionally, the CRD setup is applied to determine the total bulk loss of (58 ± 25) ppm/cm in fused silica at λ = 675 nm by measuring a thickness series.
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Ch. Mühlig, G. Schmidl, J. Bergmann, W. Triebel, "Characterization of high reflecting coatings and optical materials by direct absorption and cavity ring down measurements", Proc. SPIE 7102, Optical Fabrication, Testing, and Metrology III, 71020T (25 September 2008); doi: 10.1117/12.797679; https://doi.org/10.1117/12.797679
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