title: Femtosecond versus picosecond laser machining of nano-gratings and micro-channels in silica glass.
abstract: The ability of 8 picosecond pulse lasers for three dimensional direct-writing in the bulk of transparent dielectrics is assessed through a comparative study with a femtosecond laser delivering 600 fs pulses. The comparison addresses two main applications: the fabrication of birefringent optical elements and two-step machining by laser exposure and post-processing by chemical etching. Formation of self-organized nano-gratings in glass by ps-pulses is demonstrated. Differential etching between ps-laser exposed regions and unexposed silica is observed. Despite attaining values of retardance (>100 nm) and etching rate (2 μm/min) similar to fs pulses, ps pulses are found unsuitable for bulk machining in silica glass primarily due to the build-up of a stress field causing scattering, cracks and non-homogeneous etching. Additionally, we show that the so-called "quill-effect", that is the dependence of the laser damage from the direction of writing, occurs also for ps-pulse laser machining. Finally, an opposite dependence of the retardance from the intra-pulse distance is observed for fs- and ps-laser direct writing.
authors.affiliation: Optoelectronics Research Centre, University of Southampton, SO17 1BJ, United Kingdom. coc@orc.soton.ac.uk
authors.forename: Costantino
authors.initials: C
authors.lastname: Corbari
authors.forename: Audrey
authors.initials: A
authors.lastname: Champion
authors.forename: Mindaugas
authors.initials: M
authors.lastname: Gecevičius
authors.forename: Martynas
authors.initials: M
authors.lastname: Beresna
authors.forename: Yves
authors.initials: Y
authors.lastname: Bellouard
authors.forename: Peter G
authors.initials: PG
authors.lastname: Kazansky
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D005898:Glass / Q000737:chemistry / Q000528:radiation effects; D007834:Lasers; D049329:Nanostructures / Q000737:chemistry* / Q000528:radiation effects* / Q000648:ultrastructure; D012031:Refractometry / Q000295:instrumentation*; D012822:Silicon Dioxide / Q000737:chemistry* / Q000528:radiation effects*; D013499:Surface Properties / Q000528:radiation effects
chemical_list: D012822:Silicon Dioxide