10 July 2012 Wavelength and temperature dependence of continuous-wave laser absorptance in Kapton® thin films
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Abstract
Optical properties and laser damage characteristics of thin-film aluminized Kapton® were investigated. Spectral absorptance of virgin and irradiated samples was measured from the Kapton side of multilayered insulation over 0.2 to 15 µm wavelengths at both room temperature and 150°C. The laser-damage parameters of penetration time and maximum temperature were then measured in a vacuum environment at laser wavelengths of 1.07 and 10.6 µm. Differences in damage behavior at these two wavelengths were observed due to differences in starting absorption properties at these wavelengths. During laser irradiation, the Kapton thin film was observed with a calibrated FLIR® thermal imager in the 8 to 9.2 µm band to determine its temperature evolution. Spectral radiance throughout the mid- and long-wave infrared was also observed with a Fourier transform spectrometer, allowing temperature-dependent spectral emittance to be determined. Kapton emittance increased after the material heated past approximately 500°C, and continued to increase as it cooled posttest. This evolving temperature-dependent spectral emittance successfully predicts the increasing absorptance that led to shortened penetration times and increased heating rates for the 1.07 µm laser. For tests with constant absorptance and no material breakdown, a simplified one-dimensional thermal conduction and radiation model successfully predicts the temporally evolving temperature.
© 2012 Society of Photo-Optical Instrumentation Engineers (SPIE)
William Palm, Michael A. Marciniak, Glen P. Perram, Kevin C. Gross, William F. Bailey, Craig T. Walters, "Wavelength and temperature dependence of continuous-wave laser absorptance in Kapton® thin films," Optical Engineering 51(12), 121802 (10 July 2012). https://doi.org/10.1117/1.OE.51.12.121802 . Submission:
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