Periodic structuring of metallic surfaces using picosecond laser systems

The laser has gained significant attention in the field of surface texturing due to its numerous benefits over competing processes. A peculiar effect of the laser observed when processing under specific circumstances close to the material ablation threshold is self aligning ripple-like structures, known commonly as laser induced periodic surface structures (LIPSS). Research surrounding the ultrashort pulse production of LIP SS has identified potential for their application as a direct texturing tool. Femtosecond laser systems are not currently applicable to industrial use due to low throughput as a result of the complex nature of femtosecond pulse production. With their improved simplicity and throughput potential, picosecond laser systems are emerging as a more promising choice for industrial laser applications. This thesis aims to gain an understanding of LIPSS production with 10, 20 and 80 picosecon~ pulses in order to allow generation of these features at throughput levels more fitting to industrial applications. Detailed experimentation of the production of LIPSS under varymg processmg parameters including pulse length, pulse energy, traverse speed, traverse direction, and incident angle has been carried out. Results showed significant dependence upon incident intensity, pulse number, beam profile and intensity distribution. LIPSS threshold observation revealed evidence that suggested heating played an important role in the LIPSS generation mechanism demonstrated within this thesis. An investigation into the production of LIPSS with shaped beam profiles and intensity distributions through the implementation of a Spatial Light Modulator (SLM) has also been carried out. A square flat top beam has been successfully recreated at the sample surface and showed potential for improvement of LIPSS uniformity in comparison to a common Gaussian beam. Finally, a number of potential applications for LIPSS have been considered. This included consideration of contact angle alteration, security marking, control over cell growth and the incorporation of LIPSS within the common injection moulding process.EThOS - Electronic Theses Online ServiceGBUnited Kingdo