Analysis of a heat wave induced by laser radiation absorption in an optical fiber on the basis of a 2D nonstationary heat conduction equation

A heat wave resulting from the absorption of laser radiation in the core of an optical fiber is studied using a nonstationary 2D heat conduction equation. The velocity of the wave as a function of the laser intensity is determined, and the threshold intensity generating the heat wave is calculated. At high intensities, the velocity of the wave can be qualitatively described by a well-known formula from combustion theory; i.e., the velocity is shown to be proportional to the square root of the radiation intensity. The analytical threshold laser intensities closely agree with the available experimental data.