Side lobe suppression of a Bessel beam for high aspect ratio laser processing

• A method is proposed to suppress side lobes of a Bessel beam using interference.
• This method suppresses the maximum side lobe to less than 4% of the main lobe.
• The side lobe is negligible if suppressed only in the area near the main lobe.
• This method's beam has a sharper edge and longer focal depth than a Gaussian beam.
• This method could potentially apply to high aspect ratio laser processing.

Bessel beams can be used for high aspect ratio laser drilling and for eliminating the need to precisely position materials along the propagation direction during laser drilling and cutting. However, Bessel beams have side lobes that can damage the materials subjected to these beams. This paper discusses optical suppression of side lobes. A method is proposed to suppress these side lobes, and the method is based on interference between two Bessel beams with different wave vectors. The effectiveness of this method is confirmed both theoretically and experimentally by realizing a superposed Bessel beam; using a He–Ne laser (λ = 633 nm) and an annular binary aperture placed in front of a convex lens, this beam has a 1/e2 radius of 44 μm.