A simple experimental setup is described that facilitates accurate measurements of the temperature-dependent water absorption coefficient in the mid-infrared spectral region. With this setup, the absorption of holmium and thulium laser radiation in water was quantified to a precision of 0.5%. In the 20–100 °C temperature range, a linear decrease of the absorption coefficient with temperature is observed. The slope coefficients amount to −0.104 ± 0.001 and −0.259 ± 0.003 1/(K cm) for 2090-nm holmium and 2014-nm thulium radiation, respectively. At both wavelengths, this bleaching reduces the absorption coefficients of water at 100 °C by one third when compared with room temperature. A numerical simulation shows that the variable absorption has a noticeable influence on peak temperatures in laser heating of water.
© 2002 Optical Society of America
(120.6810) Instrumentation, measurement, and metrology : Thermal effects
(170.0170) Medical optics and biotechnology : Medical optics and biotechnology
(300.1030) Spectroscopy : Absorption
(300.6340) Spectroscopy : Spectroscopy, infrared
Björn I. Lange, Tobias Brendel, and Gereon Hüttmann, "Temperature Dependence of Light Absorption in Water at Holmium and Thulium Laser Wavelengths," Appl. Opt. 41, 5797-5803 (2002)