title: Measurement of low absorption coefficients in crystals.
abstract: The measurement of the absorption coefficient of highly transparent materials using Pinnow and Rich's calorimetric technique requires that the material be fabricated into the shape of a cylindrical rod. Since crystalline materials are more readily fabricated into rods with a square cross section, Pinnow and Rich's calorimetric technique is extended to such samples. This is accomplished by calculating the temperature distribution that is produced in a sample of material having a square cross section by the passage of a Gaussian light beam through the sample. A simple relationship between the sample surface temperature and its absorption coefficient is derived that is valid to within 2% of the exact relationship for typical conditions that occur when employing the calorimetric method. The results of a calorimetric measurement of the absorption coefficients of a single crystal of potassium dihydrogen phosphate at a wavelength lambda = 1.06 microm are reported. These are shown to be in good agreement with values reported earlier that were obtained by U. S. Averbakh, I. A. Batyrea, and V. O. Bespalov using a spectrophotometric technique.
authors.forename: D C
authors.initials: DC
authors.lastname: Johnson