In this presentation, we introduce a novel approach to machining surfaces using femtosecond (fs) UV laser systems. We explore the potential of these systems for large-area surface patterning, specifically in processing high band-gap materials like sapphire and yttrium aluminium garnet (YAG). The existing techniques are not satisfactory in terms of etch rates and accuracy, which our research is addressing. We demonstrate the use of two-beam fs-UV interference patterning to create harmonic gratings with exceptional accuracy. Key aspects include controlling the pulsed nature of the beams, optimizing pulse delay and spatial overlap, and comparing various beam splitting techniques. Our findings indicate that we can achieve sub-25 nm precision in material removal, which is a significant improvement over existing technologies. This research not only enhances the efficiency and accuracy of surface machining but also opens up new possibilities in advanced photonic applications.
We study the properties of glasses and crystals after an ultraviolet (UV) laser ablation process using 300 fs duration pulses, centered at 206 nm wavelength at the repetition rate of 50 kHz. We show that linear light absorption allows fabricating grooves with a surface roughness in the order of tens of nanometers and even sub-10 nm with low heat affected zones (HAZ) without any post-processing. We produced a single scan laser ablated microchannels’ depth, surface roughness and full width at half maximum maps based on the experimental results. These maps show relations with an overlap of laser pulses and a pulse energy and are useful when considering the working regime for specific applications. Our results depict the minimum channel bottom roughness of 8 nm in Sapphire after one scan. This value represents several times smaller roughness when compared to the nanosecond UV laser ablation. We have also studied a multi shot ablation and by evaluating our results using a scanning electron microscope (SEM) we noticed nanogratings on the walls of the craters of soda-lime and BK7 glasses with a period of 300 nm, that is bigger than the laser wavelength (206 nm). We also show that a precise surface micro patterning can be achieved with our experimental setup. Finally, our theoretical fluence distribution optimization provides a precise fabrication parameters estimate for a small surface roughness condition.
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