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15LM-P-10
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LASER-MATTER INTERACTION
Picosecond laser-induced micro- and nano-structures on Ti surface
F. Tojinazarov1,2, E. Ibragimova1, Kh. Nazarov1, N. Iskandarov1
1- Center for Advanced Technologies, 3A, University st., 100174 Tashkent, Uzbekistan 2- Ajou University in Tashkent, 113, Asalobod street, 100204 Tashkent, Uzbekistan
Enhancement of material surface functionality using short and ultrashort laser pulses has been developed due to their applications in micro- and nanotechnology such as lithography, high-density data storage, micromachining for microelectronics, surface color marking. The surface nano/micro structure was found to exhibit a regular pattern under the appropriate conditions, and this is known as LIPSS (laser induced periodic surface structures). The characteristics of LIPPS as a function of laser parameters such as polarization, fluency, wavelength, and superimposed pulse number have been investigated [1-3]. The micro and nano-structures formed on the surface have a significant impact on optical and mechanical surface properties. The morphology of both microstructures and nanostructures increases the absorption due to the geometric light-trapping effect and generates multiple internal reflections [4].
In this work we present study of LIPPS on titanium surface by dynamic laser processing. Sample is placed on a movable 3D stage allowing vary the scanning speed and step. An electromechanical shutter is used to control the number of laser pulses or to block the laser beam in scanning. A 1064 nm picosecond laser (EKSPLA PL2230) operated with a pulse duration of 28 ps and a repetition rate up to 50 Hz. The beam was focused with a plan-convex lens with the focal length of 75 mm. Laser-induced morphological and composition changes were monitored by scanning electron microscopy (SEM&EDX, EVO MA10, Zeiss). The dependence of the laser parameters on the modified target surface was determined. We also observed structural colourisation on the titanium sample which appears golden and blue. Fig.1 (a) shows SEM image and golden glitter appearance of Ti. Spectral differences between blue and golden titanium as function of wavelength were analysed using a UV-VIS-NIR spectrophotometer (UV-3600 Shimadzu). Fig.1 (b) shows reflectance spectra of Ti before and after processing with laser fluency of 3.75 J/cm2, the most reduced reflection was about 10% in the range of 300 and 330 nm.
Fig. 1 (a) SEM and inserted optical images of Ti sample modified with 100 mm/min scanning speed at 1064 nm wavelength, (b) Reflectance spectra of Ti: black - before, red - after the laser processing.
[1] S. Maragkaki, et.al.,Wavelength dependence of picosecond laser-induced periodic surface structures on copper, Applied Surface Science, 417, 88-92, (2017).
[2] G.Lazzinia, L. Romolia, F.Tantussib, F.Fuso, Nanostructure patterns on stainless-steel upon ultrafast laser ablation with circular polarization, Optics and Laser Technology, 107, 435-442, (2018).
[3] J. Bonse, S.V. Kirner, J. Krüger, Laser-Induced Periodic Surface Structures (LIPSS) (Springer), (2020).
[4] A. Y. Vorobyev,Chunlei Guo, Multifunctional surfaces produced by femtosecond laser pulses, Journal of Applied Physics 117, 033103 (2015).
