Laser heating of thick layers through the backwards, self-sustained propagation of a steep and steady state thermal front

Aplinov, Presvert No. 9, 38113 Veurey-Voroize, France

Corresponding author: michel.bruel@aplinov.com

Received: 26 September 2008
Revised: 30 October 2008
Accepted: 9 December 2008
Published online: 25 December 2008

Abstract

We investigate theoretically a mode of heating layers using a laser beam. In this mode thermal energy, the temperature of the layer, propagates in a steady-state self sustained fashion from the bottom of the layer towards the surface and may exhibit a very steep front. The propagation exhibits a constant speed, related to the intensity of the power flux. To achieve this heating mode the absorption coefficient has to remain low in low temperatures and increase rapidly as a function of temperature in higher temperatures. Additionally, a significant temperature increase must be generated to trigger this propagation mode, for example through the presence of a strongly absorbing layer beneath the transparent layer. The mode is well suited to semiconductors, especially silicon. A few examples of applications are proposed.