High-damage-threshold sidelobe-suppressed Bessel beam generator for laser processing applications

Bessel beams, characterized by an extended depth of focus and non-diffracting propagation, have been extensively employed in areas such as laser processing and optical imaging. However, their applications in precision machining are hindered by high-energy sidelobes that cause unintended damage to non-target regions, increasing surface roughness and reducing accuracy. Conventional sidelobe suppression techniques, such as the use of axicons combined with phase plates or annular apertures, generally involve complex setups, exhibit high alignment sensitivity, and are unsuitable for high-power lasers. To address these limitations, we realize a high-damage-threshold metasurface for generating sidelobe-suppressed Bessel beams (SSBB). The design employs a hybrid modulation strategy that integrates a simulated-annealing-optimized binary phase ring with an axicon phase. The metasurface is fabricated in silica glass via femtosecond laser direct writing, where laser-induced birefringent nanopores enable geometrical phase modulation. The prepared metasurface exhibits high threshold characteristics and a conversion efficiency of 96.3%. The metasurface-generated SSBB shows a first sidelobe peak intensity of only 5.2% of the main lobe—representing a 72.3% reduction compared to conventional Bessel beams (18.8%). The generated SSBB demonstrates superior machining quality in the drilling of silica glass. This approach provides an integrated solution to the sidelobe issue in Bessel beams and holds significant potential for advanced manufacturing applications, including semiconductor packaging and cooling hole drilling in aero-engine turbine blades.