Temperature Rise Mechanics Of Thin Metal And Semiconductor Films Irradiated By Femtosecond Pulse Laser

Along with the continuous progress of the Q-switching and model-locking technologies, the durations of ultra-short optical pulses have been compressed successfully from ns and ps to the order of fs. And supported by the amplifier technologies of the chirp pulses, the peak power of laser pulses have been successfully increased by several orders. As a result, the research on the interaction between laser and materials has been advanced to completely new stage.1. femtosecond pulse damage to metalA new dual-hyperbolic two temperature model is established. One self-adaptive forward finite differential numerical solving method with artificial viscosity treatment is utilized. A calculation program is written based on standard C language and run in an ordinary PC. The spatio-temporal temperatures and heat flux distributions of electrons and lattices, in the specified metal films, are calculated and discussed. The chief conclusions may be shown as follows:(1) irradiated by the laser pulse with parameters of t_p=0.14ps and J₀=4700J/m², the damage threshold of golden films with 200nm thickness, calculated by us, is about 4700J/m², and the experimental result got by Al-Nimr et al, in the same parameters, is 0.43±0.04J/cm². The agreement between the theory prediction and experiment result verifies the validity of our model.(2) Our further calculations, have verified that the influence of capacity of electrons, on the electron temperature distributions and the electron-lattice balance time, is very strong. But the influence of the thermal conduction is very little and may be neglected. And the influence of energy coupling procedure of electron-lattice, to the temperature distributions of lattice, is much lets important than that of thermal conduction procedure to the lattice.(3) There are obvious sharp peak structures in the curves of heat flux and temperature of electrons. And except for the front surface, there are tow-sharp-peak structures in the heat flux curves.(4) The time when the heat flux of electrons reaches its maximum is a little bit earlier than that of temperature of electrons. And in the same depth, the heat flux of the electrons is lager while its temperature is higher.In addition, although the structure of heat flux in the lattice is simpler than that in the electrons, one should pay more attention to that, in the range of the optical absorption depth, the heat flux is larger if the depth is larger. This phenomenon can not be explained by the classic Fourier thermal conduction theories. The main reason is arise from the complexity of the system, such as the large non-linearity of the interaction behaved electrons and lattices. The reveal of the concrete reasons is waiting for deeper theory analysis and numerical calculation research.2. Femtosecond pulse damage to semiconductor materialsBased on a self-consistent field modal is established in this chapter. The theory fundamental of the model is relaxed timing approximation of Boltzmann equations. The parameters we take care of in the model mainly are the densities and currents of electrons and holes, energy currents and energy densities, the temperature of electrons and lattices. And the relations of the parameters above is simulated and calculated in the dissertation.