Transient Thermal Modeling of Pulsed Laser Irradiation of a Low Absorbing Multilayer Device Using a 2D Model

In this paper, we report the heat generation and temperature field in a multilayer device consisting of thin and weakly absorbing materials subject to pico-second to nano-second pulsed-laser heating. The interference effects due to the internal reflection and refraction are considered. A tracking method based on electromagnetic optics and wave optics is used to determine the two-dimensional electrical and magnetic fields. These fields are then used to calculate the heat generation and the accompanying temperature distribution. For demonstration, we apply this method to determine the temperature field in a ZnSe interference filter subject to inclined laser incidence on its side. The simulation results show strong localized heating in a narrow region along the side where laser power is incident. The localized heating produces several high power spots, aligned obliquely to the side surface. The results show that the pure absorption model is not valid for even small incident angles. Surface absorption may be a valid approximation but the heat flux distribution is not uniform.