High-aspect ratio damage and modification in transparent materials by tailored focusing of femtosecond lasers

We discuss studies of laser damage inside various transparent materials (glasses, polymers, sapphire, diamond) caused by femtosecond lasers at 515, 800, and 1030 nm, with nJ to mJ pulse energies, single-shot to 2 MHz repetition rates, single and 10 ns burst-mode pulses, chirped pulses, and linear, circular, and radial beam polarizations. Experiments have created high-aspect damage features and voids using aberration-controlled focusing, axicon-formed Bessel beams with <1 μm diameter central lobes extending hundreds of microns through the materials, and tightly focused lines (~1 μm × <100 μm). Mechanisms include self-focusing, filamentation, and material expansion/compaction and expulsion.