By solving thermal conduction and thermo-elastic equations with an integral-transform method, a theory to describe the three-dimensional temperature and deformation distributions in an optical coating sample irradiated by a pulsed or square-wave modulated laser is developed for both transient and steady state cases. The theoretical simulations are compared with corresponding results of the finite-element method in time and space domains and good agreements are obtained. In addition, the influences of heating-beam radius and modulation frequency on the temperature and deformation distributions are discussed. Applications of the theoretical model to absorptance and deformation measurements of optical coatings are discussed.