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Annular beam analysis of an optical trepanning system

An annular beam provides a new laser drilling mechanism, that we refer to as "optical trepanning". Based on ray tracing techniques, a refractive axicon system has been designed to transform an input Gaussian laser beam into an annular beam with an appropriate irradiance profile. The properties of the resulting annular beam are investigated in this paper. The diffraction patterns were measured, showing that a collimated annular beam can be obtained using a refractive axicon system. However, due to spherical aberration effects, the focused annular beams possess altered irradiance profiles with different focusing lenses. The effects of spherical aberration on the focused annular beam are also investigated.