title: Evolution of hole shape and size during short and ultrashort pulse laser deep drilling.
abstract: A detailed study of the influence of the pulse duration, from the femtosecond to the nanosecond regime, on the evolution of the hole shape and depth during percussion drilling in silicon is presented. Real-time backlight imaging of the hole development is obtained for holes up to 2 mm deep with aspect ratios extending to 25:1. For low pulse energies, the hole-shape and drilling characteristics are similar for femtosecond, picoseconds and nanosecond regimes. At higher pulse energies, ns-pulses exhibit slower average drilling rates but eventually reach greater final depths. The shape of these holes is however dominated by branching and large internal cavities. For ps-pulses, a cylindrical shape is maintained with frequent small bulges on the side-walls. In contrast, fs-pulses cause only a limited number of imperfections on a tapered hole shape.
authors.affiliation: Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Jena, Germany. sven.doering@uni-jena.de
authors.forename: Sven
authors.initials: S
authors.lastname: Döring
authors.forename: John
authors.initials: J
authors.lastname: Szilagyi
authors.forename: Sören
authors.initials: S
authors.lastname: Richter
authors.forename: Felix
authors.initials: F
authors.lastname: Zimmermann
authors.forename: Martin
authors.initials: M
authors.lastname: Richardson
authors.forename: Andreas
authors.initials: A
authors.lastname: Tünnermann
authors.forename: Stefan
authors.initials: S
authors.lastname: Nolte
mesh_terms: D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007834:Lasers; D008422:Materials Testing / Q000379:methods; D010783:Photometry / Q000379:methods*