Maximum depth of penetration of a laser beam in an absorbing medium

A model of "dagger" melting of metals by high-power light beams is considered. An allowance is made for multiple reflections of the rays from the walls of a cavity formed in a sample and the maximum depth of penetration of a laser beam into a metal is calculated. It is shown that the greatest depth of penetration and the largest ratio of the depth to the diameter are obtained if the laser beam polarization corresponds to axially symmetric magnetic modes in a metal waveguide, i.e., when the electric field vector is parallel to the side walls of the cavity.