Laser ablation using a nanosecond optical vortex pulse

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. As a light source, we used a conventional Q-switched ns-YAG laser generating a fundamental Gaussian beam with a wavelength of 1064 nm and pulse duration of -40 ns. OVs pulses were produced by modulating spatial phase azimuthally using a spiral phase plate technique. We focused OVs pulses onto tantalum (Ta) plates as target samples, with spot sizes of 100 mum. After a single-shot- pulse laser ablation, surfaces of Ta were observed by a confocal laser-scanning microscope. For the Gaussian pulse, the processed surface was rough with higher spatial frequencies. A lot of debris flied radially around the outer circumference of the processed surface. In good contrast to this, for the OV pulse, better-processed surface was observed with lower spatial frequencies. Typical length of flied debris became shorter and numbers of flying debris were reduced in comparison with the case of the Gaussian pulse. This is considered to be due to the effect of OAM in the ablation process.