Self-focusing and waveguide propagation of radiation in the case of deep penetration of a metal by a laser beam

An investigation is made of the characteristic features of self-focusing of radiation in the case of formation of a crater in an opaque medium (metal). It is shown theoretically that a considerable increase in the energy density at the bottom of a crater is possible because of the excitation of whispering gallery waveguide modes in the crater. A self-similar regime of crater formation is considered. A study is made of the influence of the roughness of crater walls on the maximum depth of penetration of metals by laser beams with different polarizations. The results are given of an experimental determination of the distribution of electromagnetic energy in narrow capillary tubes.