TY - GEN

T1 - Laser calorimetric absorptance testing of samples with varying geometry

AU - Balasa, Istvan

AU - Jensen, Lars

AU - Ristau, Detlev

PY - 2013/11/14

Y1 - 2013/11/14

N2 - During the 1990s the International Standard for absorptance testing of optical coatings was developed. Based on the method of laser calorimetry and after years of theoretical and empirical work, ISO 115511 was revised and published in its current version in 2003. Laser calorimetry is based on the measurement and evaluation of the temperature increase caused by absorption in the sample exposed to laser radiation. In dependence on the thermal diffusivity of the sample, a temperature distribution develops in the irradiated sample. Therefore, finding a correlation of temperature increase and absorption becomes a complex task. This challenge was met by keeping the sample geometry to a standard size and simulating the thermal distribution for a number of optical materials. By this, LZH developed a calorimetric test set-up that offers fully calibrated absorptance values for sample diameters of 25 mm (or 1 inch) with a total error of below 13 % and a relative measurement error of below 5%. However, this technique is limited to the mentioned sample geometry. This work presents a new approach to adjust the measurement configuration to numerous sample sizes of standard circular laser components. Finite element analysis and experimental verification is presented for exemplary values of the samples diameters. Based on a new sample mount concept, this procedure allows utilizing all flexibility in test wavelength and angle of incidence, combined with the sensitivity level sufficient for current optical materials.

AB - During the 1990s the International Standard for absorptance testing of optical coatings was developed. Based on the method of laser calorimetry and after years of theoretical and empirical work, ISO 115511 was revised and published in its current version in 2003. Laser calorimetry is based on the measurement and evaluation of the temperature increase caused by absorption in the sample exposed to laser radiation. In dependence on the thermal diffusivity of the sample, a temperature distribution develops in the irradiated sample. Therefore, finding a correlation of temperature increase and absorption becomes a complex task. This challenge was met by keeping the sample geometry to a standard size and simulating the thermal distribution for a number of optical materials. By this, LZH developed a calorimetric test set-up that offers fully calibrated absorptance values for sample diameters of 25 mm (or 1 inch) with a total error of below 13 % and a relative measurement error of below 5%. However, this technique is limited to the mentioned sample geometry. This work presents a new approach to adjust the measurement configuration to numerous sample sizes of standard circular laser components. Finite element analysis and experimental verification is presented for exemplary values of the samples diameters. Based on a new sample mount concept, this procedure allows utilizing all flexibility in test wavelength and angle of incidence, combined with the sensitivity level sufficient for current optical materials.

KW - Absorption

KW - Contamination

KW - High power laser

KW - Laser calorimetry

KW - Metrology

KW - Optical thin films

KW - Substrates

KW - Ultrafast laser optics

UR - http://www.scopus.com/inward/record.url?scp=84892633663&partnerID=8YFLogxK

U2 - 10.1117/12.2030273

DO - 10.1117/12.2030273

M3 - Conference contribution

AN - SCOPUS:84892633663

SN - 9780819497536

T3 - Proceedings of SPIE - The International Society for Optical Engineering

BT - 45th Annual Laser Damage Symposium Proceedings - Laser-Induced Damage in Optical Materials

PB - SPIE

T2 - 45th Annual Laser Damage Symposium - Laser-Induced Damage in Optical Materials: 2013

Y2 - 22 September 2013 through 25 September 2013

ER -