High-Speed Photographs of Laser-Induced Heating

This Communication presents some high-speed photographs showing the effects of high-energy, focused laser beams striking targets of steel, brass, and aluminum. For the light flux densities used, these photographs seem to support recent speculation1–3that the absorption of intense laser radiation will heat the material at some depth below the surface to its vaporization temperature before the material at the surface has absorbed its latent heat of vaporization. This is thought to induce a pulse of high pressure in the underlying material and to result in the emission of the vaporized material similar to a chemical explosion.