Although laser drilling of carbon fibre-reinforced polymer (CFRP) composites offers the advantages of zero tool-wear and avoidance of fibre delamination compared with mechanical drilling, it consumes considerably more energy during the drilling process. This research shows that by using a new, stepped parameter parallel ring laser hole drilling method, an energy saving of 78.10% and an 18.37 gCO₂ reduction for each hole, while improving productivity by more than 300%, can be achieved in laser drilling of 6 mm diameter holes in CFRP sheets of 2 mm in thickness, compared with previous laser drilling methods under the same drilling quality. The key reason for this is an increase in energy input to the inner rings enabling more rapid removal of the material, while the lower energy input for the outer ring provides a shielding trench to reduce the heat loss into the parent material. The results are compared with single-ring laser drilling and multiple-ring laser drilling with constant processing parameters, and a discussion is given on comparing with mechanical drilling and future prospects, including a combined mechanical drilling and laser pre-scribing process.

This study investigates the fabrication of blind holes in Inconel 718 alloy using a quasi-continuous wave (QCW) laser under varying pulse numbers. The geometric features, spatter formation, inner wall morphology, and microstructures of the drilled holes were systematically analyzed. Experimental results demonstrate that increasing the number of laser pulses from 1 to 13 significantly improves the hole depth, ranging from 565.09 to 3952.54 μm, achieving a maximum depth-to-diameter ratio of 9.5. Shallow holes exhibited optimal morphology with clean edges and smooth inner walls, whereas deeper holes displayed a composite structure consisting of inverted cone (upper), cylindrical (middle), and spindle-shaped (lower) sections. The thickness of the recast layer increased along the depth as the pulse numbers rose. Microstructural analysis revealed that the recast layer contained refined grains, with kernel average misorientation analysis indicating high residual stress within this layer. The hardness of the recast layer, measured at 2.13 GPa, was notably lower than that of the base material (4.49 GPa), primarily due to the depletion of the strengthening phase and the formation of the Laves phase. This work provides an in-depth understanding of the characteristics and mechanisms of QCW laser drilling in Inconel 718 alloy, offering valuable insights to optimize the laser processing parameters for industrial applications.

Nanopattering of silicon substrates using near-field enhancement by particle-lens arrays in a chemical solution is presented for the first time. Both experimental and theoretical investigations have been carried out to understand the properties of the nanopatterns produced. The obtained results proved that the developed nanofabrication technique is a flexible method for precise surface nanopatterning over large area surface. Novel nanostructures such as nano-bump and ring arrays, that previously not possible to be produed using the particle-lens arrays, have been demonstrated using this technique. A close-packed monolayer of SiO2 spheres (r= 250 nm) was directly formed onto the silicon surface by self-assembly, and a 248nm wavelength KrF excimer laser was used to irradiate the samples. The theoretical modeling of the optical near-field is based on extended Mie theory. The effect of the laser fluence and assisted chemicals is studied. Due to the focusing of the particle lens, a reaction between the chemical solution and substrate can be induced in the locally high energy region. As a result, a lower laser fluence than the ablation threshold of bulk silicon can be used to generate nano-scale features.