Authors: A K Türkoğlu T Ersoy F Canbaz S Akturk
Publish Date: 2012/06/06
Volume: 108, Issue: 4, Pages: 935-941
Abstract
We investigate the dynamics of femtosecondlaser drilling of metals both theoretically and experimentally by taking into account waveguidelike behavior of ablated cavities In particular we show that cylindrical holes generated during laser ablation of metals act like hollow optical waveguides Since the drilling is generally achieved by a large number of consecutive pulses each pulse is first guided through the channel formed by the previous pulses and at the end of the channel it is absorbed by the metal making its own contribution to ablation The ablation stops at maximum depth when attenuation in the cavity reduces the pulse fluence to the ablation threshold We use waveguide theory to calculate attenuation constants and perform an iterative calculation to model pulsebypulse ablation We also performed detailed experiments and compare the results with the theoretical findings When only absorption losses are included the waveguide model predicts significantly deeper structures On the other hand when we include scattering losses caused by nanostructures formed on the cavity walls quantitative agreement with experiments is achieved The waveguide model is particularly effective at fluences close to ablation threshold and it can explain several behaviors such as evolution of the depth per pulse and effect of the incoming pulse energy in different focusing configurationsWe would like to acknowledge funding from the Scientific and Technological Research Association of Turkey TÜBİTAK under the Grant 110T330 and Turkish Academy of Sciences TÜBA GEBİP We thank Thin Film Laboratory of ITU Physics Department SEM Laboratory of ITU Materials Science Department and UNAM at Bilkent University for assisting in various stages of characterization experiments
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