ULTRAFAST-LASER DRIVEN MICRO-EXPLOSIONS IN TRANSPARENT MATERIALS

We initiate micro-explosions inside fused silica, quartz, sapphire, an d other transparent materials using tightly focused 100 fs laser pulse s, In the micro-explosions. material is ejected from the center, formi ng a cavity surrounded by a. region of compacted material, We examine the resulting structures with optical microscopy, diffraction, and ato mic force microscopy of internal cross sections. We find the structure s have a diameter of only 200-250 nm, which we attribute to strong sel f-focusing of the laser pulse. These experiments probe a unique regime of light propagation inside materials at intensities approaching 10(2 1) W/m(2), the electron ionization that accompanies it, and the materi al response to extreme pressure and temperature conditions. Tile micro -explosions also provide a novel technique for internal microstructuri ng of transparent materials. (C) 1997 American Institute of Physics.