Laser ablation using a nanosecond optical vortex pulse

Optical vortices (OVs) are the beams, having helical wavefronts due to their phase distribution of mϕ (m; integer, ϕ; azimuthal angle) in transverse plane [1]. Figure 1 shows typical images of a helical wavefronts and an intensity profile. OVs have annular intensity profiles resulting from on-axis phase singularity, and also have orbital angular momentum (OAM) of light resulting from their helical wavefront, that is, rotational optical flux. Using these unique characters, OVs have been employed in various fields, for example, microstructure rotation in laser tweezers and spanners [2]. In the present paper, we apply OV pulses to laser ablation in material processing for the first time, and we also investigate the effect of the OAM on ablation dynamics.