Measuring the infrared absorption in thin film coatings

Traditionally, the optical absorption in thin dielectric films has been obtained by comparing the absorption in coated and uncoated substrates. A new technique has been developed in which the absorption of the film is obtained directly without resorting to comparison or difference methods. This method relies on the separation of surface and bulk heat that results from laser calorimetric measurements on long, bar-shaped samples. Single layer films of As(2)S(3), CaF(2), ThF(4), and PbF(2) were deposited on a KCl bar, and the absorption coefficient of each film was extracted from the slopes of the temperature-time curves.