Femtosecond-laser processing incubation in Diamond-like carbon

Diamond-like carbon (DLC) has been commercialized as an advanced material for combining diamond and graphite properties with other material systems, with ease of processing and reduced costs. DLC has been broadly studied as an interesting material for applications ranging from biology to optics, passing through mechanics and electronics. Hence, for given applications, complex patterning of DLC is required, which can be accomplished by conventional lithographic approaches, as well as laser structuring. In this way, this paper focuses on studying the incubation process, the dependence of the threshold fluence with the number of irradiated pulses, on the fs-laser microstructuring of DLC films. We determined a single pulse fluence of (1.0 ± 0.1) J/cm 2, a value that decreases to a plateau of (0.13 ± 0.04) J/cm 2 for a large number of pulses. The slow evolution of the fluence threshold with the number of pulses indicates a low incubation parameter, such that a large number of pulses is required to damage the material. By modeling the single-pulse damage threshold fluence considering multiphoton and avalanche ionization, we were able to estimate a two-photon absorption cross-section for DLC of (1.5 ± 0.5) × 10 −60 m 4 s 1 photon −1, which is consistent with the one known for diamond. Finally, Raman spectroscopy of the fs-laser processing DLC sample indicates a decrease of the sp 3 fraction and a more ordered phase.