The Laser Zentrum Hannover e.V. (LZH; Hannover, Germany; www.lzh.de) has developed a laser calorimeter that is able to measure the absorption of light in the material. Specific advantages of the device are its high sensitivity, absolute calibration, and a wide spectral range of the test wavelength.
By using a precise temperature measurement of the material, the laser calorimeter is able to detect an absolute absorption of <1 ppm (one millionth of the irradiated laser power). This preciseness can detect the smallest absorption data deriving from surfaces, coatings, or impurities in the material. Absorption measurements with laser wavelengths between 193 nm and 2000 nm are possible. In addition, the range between 670 nm and 2200 nm is completely accessible. Measured data can be used to optimize the material, machining, and coating processes. Thus, continuous improvement of respective characteristics of laser optics is possible.