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ISSN Online: 2377-424X

ISBN Print: 1-56032-797-9

International Heat Transfer Conference 11
August, 23-28, 1998, Kyongju, Korea

NUMERICAL SOLUTION FOR THE DIFFUSION OF HIGH INTENSITY, ULTRASHORT LASER PULSES WITHIN METAL FILMS

Get access (open in a dialog) DOI: 10.1615/IHTC11.410
pages 241-246

Аннотация

The advancement of intense ultrashort pulse lasers has been a focus of the optoelectronics industry for over a decade. This has brought considerable attention to the energy transport processes occurring in materials during and after short pulse laser material interaction. Since the electrons and lattice are not in thermal equilibrium until long after the pulse duration, the classical heat diffusion equation is no longer valid. This phenomena, called non-equilibrium heating, has been studied by numerous investigators. The Parabolic Two Step (PTS) and Hyperbolic Two Step (HTS) models were proposed to describe this behavior. The solution of the PTS and HTS equations require some knowledge of the temperature dependence of the thermophysical parameters. In general, the electron heat capacity is assumed to be a linear function of the electron temperature; the thermal conductivity is treated either as constant or as dependent on the ratio of the electron to lattice temperature; and both the electron-phonon coupling factor and lattice heat capacity are assumed constant. In situations where the electron temperature is much much less than the Fermi temperature, these assumptions are valid. However, as the electron temperature increases the thermal conductivity is reduced due to electron-electron scattering. Also, if the electron temperature is high enough in the transition metals (~3400 K for gold), the d shell electrons contribute to the electron heat capacity and the electron-phonon coupling factor. This paper presents the solution of the Parabolic Two Step model for applications that induce high electron temperatures, accounting for the temperature dependence of the electron heat capacity, thermal conductivity, and the electron-phonon coupling factor.