Publication database

The growing demand for flexible, high-quality fabrication of free-form micro-optics drives the development of laser-based fabrication techniques for both the shape formation and surface polishing of optical elements. In this paper, we performed a thorough and systematic study on fused silica glass ablation using 10 ps and 320 fs duration pulses. Ablation processes for both pulse durations were optimized based on the measurements of the removed material layer thickness and surface roughness, and by analyzing the topographies of ablated cavities to remove material layers as thin as possible with minimum surface damage. Our findings demonstrate higher process resolution and surface quality for femtosecond pulses. Ablation of pre-roughened glass reduced the minimal removable glass layer thickness well below the 1 μm mark for both pulse durations, improving the process resolution. The minimal removable glass layer thickness was 14 times smaller for the femtosecond pulses, with up to 4.5 times lower surface roughness compared to samples processed with picosecond pulses. On the other hand, results revealed faster glass removal rates with picosecond pulses. In the end, arrays of microlenses were fabricated with both pulse durations and subsequently polished with a CO2 laser. Results revealed higher performance of microlenses fabricated with femtosecond pulses, providing better focusing capabilities and lesser beam scattering. Finally, this study demonstrated the successful fabrication of free-form optical elements with femtosecond and picosecond pulses, demonstrating the versatility and the potential of laser-based techniques.

The cutting quality and strength of strips cut with femtosecond-duration pulses were investigated for different thicknesses of borosilicate glass plates. The laser pulse duration was 350 fs, and cutting was performed in two environments: ambient air and water. When cutting in water, a thin flowing layer of water was formed at the front surface of the glass plate by spraying water mist next to a laser ablation zone. The energy of pulses greatly exceeded the critical self-focusing threshold in water, creating conditions favorable for laser beam filament formation. Laser cutting parameters were individually optimized for different glass thicknesses (110–550 µm). The results revealed that laser cutting of borosilicate glass in water is favorable for thicker glass (300–550 µm) thanks to higher cutting quality, higher effective cutting speed, and characteristic strength. On the other hand, cutting ultrathin glass plates (110 µm thickness) demonstrated almost identical performance and cutting quality results in both environments. In this paper, we studied cut-edge defect widths, cut-sidewall roughness, cutting throughput, characteristic strength, and band-like damage formed at the back surface of laser-cut glass strips.

Water-assisted ultrashort laser pulse processing of semiconductor materials is a promising technique to diminish heat accumulation and improve process quality. In this study, we investigate femtosecond laser ablation of deep trenches in GaAs, an important optoelectronic material, using water and ambient air environments at different laser processing regimes. We perform a comprehensive analysis of ablated trenches, including surface morphological analysis, atomic-resolution transmission electron microscopy imaging, elemental mapping, photoluminescence, and Raman spectroscopy. The findings demonstrate that GaAs ablation efficiency is enhanced in a water environment while heat-accumulation-related damage is reduced. Raman spectroscopy reveals a decrease in the broad feature associated with amorphous GaAs surface layers during water-assisted laser processing, suggesting that a higher material quality in deep trenches can be achieved using a water environment.