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Temperature dependence of the absorption coefficient of water for midinfrared laser radiation
Author(s) -
Jansen E. Duco,
van Leeuwen Ton G.,
Motamedi Massoud,
Borst Cornelius,
Welch Ashley J.
Publication year - 1994
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/lsm.1900140308
Subject(s) - attenuation coefficient , radiation , laser , absorption (acoustics) , materials science , optics , physics , composite material
The dynamics of the water absorption peak around 1.94 μm was examined. This peak is important for the absorption of holmium and thulium laser radiation. To examine the effect of temperature on the absorption coefficient, the transmission of pulsed Ho: YAG, Ho:YSGG, and Tm:YAG laser radiation through water of 22°C, 49°C, and 70°C was measured as a function of the thickness of the water layer. From these data the absorption coefficients were determined at the three wavelengths. We found that at all three wavelengths, the absorption coefficients decreased when increasing the temperature. Second, the absorption spectrum of water was measured from 1,850–2,150 nm with a spectrophotom‐eter. It was found that the absorption peak at 1.94 p,m (at 22°C) shifts to shorter wavelengths with increasing temperatures, to 1.92 μm at 70°C. A model was developed to predict the temperature distribution incorporating the dynamic change in absorption coefficient. The temperature distributions are compared to the predictions of a model assuming constant optical properties. It is shown in this study that the dynamics of the absorption coefficient has a significant influence on the expected zone of damage and ablation parameters in the 2‐μm wavelength range. © 1994 Wiley‐Liss, Inc.