title: Time dynamics of burst-train filamentation assisted femtosecond laser machining in glasses.
abstract: Bursts of femtosecond laser pulses with a repetition rate of f = 38.5MHz were created using a purpose-built optical resonator. Single Ti:Sapphire laser pulses, trapped inside a resonator and released into controllable burst profiles by computer generated trigger delays to a fast Pockels cell switch, drove filamentation-assisted laser machining of high aspect ratio holes deep into transparent glasses. The time dynamics of the hole formation and ablation plume physics on 2-ns to 400-ms time scales were examined in time-resolved side-view images recorded with an intensified-CCD camera during the laser machining process. Transient effects of photoluminescence and ablation plume emissions confirm the build-up of heat accumulation effects during the burst train, the formation of laser-generated filaments and plume-shielding effects inside the deeply etched vias. The small time interval between the pulses in the present burst train enabled a more gentle modification in the laser interaction volume that mitigated shock-induced microcracks compared with single pulses.
authors.affiliation: RWTH Aachen University, Steinbachstraße 15, 52074 Aachen, Germany . dagmar.esser@llt.rwth-aachen.de
authors.forename: Dagmar
authors.initials: D
authors.lastname: Esser
authors.forename: Saeid
authors.initials: S
authors.lastname: Rezaei
authors.forename: Jianzhao
authors.initials: J
authors.lastname: Li
authors.forename: Peter R
authors.initials: PR
authors.lastname: Herman
authors.forename: Jens
authors.initials: J
authors.lastname: Gottmann
mesh_terms: D005898:Glass / Q000737:chemistry* / Q000528:radiation effects*; D007834:Lasers; D008420:Manufactured Materials / Q000528:radiation effects*; D008422:Materials Testing