펄스 레이저의 매질 흡수에 의해 발생하는 열 효과 시뮬레이션 및 해석에 관한 연구

Abstract

We investigated the thermal effects induced by pulsed laser absorption in an optical medium through simulations of the thermal diffusion equation. In particular, the dependences of maximum temperature increase and decay time constant on the laser pulse width, beam diameter, and absorption coefficient were examined. As the laser pulse width increased, the maximum temperature increase decreased and the decay time constant increased. It was found that the temporal behaviors of the temperature increase could be predicted by the convolution of the response function of the system with a very short laser pulse and a square pulse function corresponding to the laser pulse width. As the laser beam diameter increased, the maximum temperature increase decreased and the decay time constant increased, too. The maximum temperature increase showed the inverse square dependence on the laser beam diameter, and the decay time constant was found to be almost independent of the laser beam diameter for relatively large absorption coefficients. As the absorption coefficient increased, the maximum temperature increase increased and the decay time constant decreased. The maximum temperature increase was directly proportional to the absorption coefficient, and the decay time constant was found to be almost independent of the absorption coefficient for relatively small laser beam diameters. It is expected that the results of this study will provide valuable information for the prediction and analysis of experiments on evoking tactile sensations by using a pulsed laser executing varying laser pulse width, laser beam diameter, and wavelength.