Fabrication of large-area hole arrays using high-efficiency two-grating interference system and femtosecond laser ablation
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- Kaakkunen, J.J.J., Paivasaari, K. & Vahimaa, P. Appl. Phys. A (2011) 103: 267. doi:10.1007/s00339-011-6366-4
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We present a novel method to fabricate hole arrays by forming a four-beam interference pattern with two gratings. In this method a femtosecond laser beam is split into four and collected to interfere using two cascaded diffractive gratings. One benefit of this grating pair is that it is achromatic, because of the geometry of the grating pair, and therefore it is suitable for femtosecond ablation. Grating pairs were designed and fabricated for a standard Ti:sapphire femtosecond laser, with 800-nm central wavelength, so that the interference pattern generates holes with less than 1-μm diameter. Holes with this size diffract with a colorful visual appearance in the visible wavelength range and therefore these structures are suitable for security, authentication and decorative marking. We show that this method is suitable for fast ablation of hole arrays in both silicon and steel.