CC BY
11LM-O-10
LASER-MATTER INTERACTION
Drilling of micro-hole grids in quartz crystals with ultraviolet picosecond
laser
E.M. Ibragimova1,2, A.A. Sapaeva1, N.E. Iskandarov1, F.M. Tojinazarov1, B.R. Sobirov1,
K.T. Nazarov1 and Z.T. Azamatov1
1Center for Advanced Technologies, Tashkent, Uzbekistan; institute of Nuclear Physics Academy of Sciences, Tashkent, Uzbekistan
ibragimova@inp.uz
Ultrafast laser pulse of a few ^J energy tightly focused inside the bulk of a transparent solid generates ~ MJ/cm3 energy density within a micro-scale focal volume; ultraviolet femtosecond lasers are used for patterning micro-grooves in glass substrates by means of laser ablation [1]. However we found that profiles of micro- and nano-holes drilled in silica glass with ultraviolet picosecond laser were changing during a few months due to viscosity of glass network [2]. To eliminate the negative effect of viscous flow, a crystalline dielectric is required for drilling stable micromembranes.
We studied various modes of drilling micro-hole grids in piezoelectric quartz crystal plates of 1 mm thickness with 10 picosecond pulses of diode pumped Nd:YAG laser at the 4th harmonics 266 nm (PL2231-50, Ekspla, Litvania). For intensive UV-absorption the samples were irradiated with 60Co y-quanta. The surface morphology of the obtained micro- and nano-holes and temporal stability of the hole profiles were studied with scanning electron microscope (SEM EVO-MAIO, Zeiss) after deposition of 5 nm Ag film for removing an induced charge. Figure 1 shows profiles and sizes of one micro-hole (a) and 6x6 grid (b), and also profiles of shock waves around each hole (a).
ALT'22
Fig. 1. Profiles of micro-holes drilled in piezo-quartz crystal with 4-th harmonics 266 nm
at a pulse energy 3 mJ (a), 14 mJ (b)
Photos taken at higher and lower magnification show an elliptic shape of each hole and asymmetric damage area around it. The local element composition (Energy Dispersion Spectrometer installed in SEM) around the holes was found to deviate from that of the reference sample: the concentration of Si decreases from 45 to 25 w%, while Carbon increases from 8 to 35w%. This effect depends on the laser pulse energy and maybe due to processes in the plasma generated in SiO2 by the focused laser beam. Fig.1a revealed radial shockwaves with the period of 5 mm. Varying the energy and number of pulses allowed us to obtain through holes in the range of diameters 0 5-50 ^m, which are suitable for grid membranes filtering or separating liquid mixtures [1]. The crystal lattice of quartz retains the shape of laser holes and frozen radial shock waves, which will allow using the picosecond laser processing to make nano-ribbed and micro-ribbed structures in the near-surface layer about a few microns for resonant tunneling photonic filters. The research is supported by Ministry of innovation development of Republics Uzbekistan.
[1] V.P. Veiko, V.I. Konov Ed. Fundamentals of laser-assisted micro- and nanotechnologies. 2014, Springer Series in materials science, vol.195.
[2] E.M. Ibragimova, A.A. Sapaeva, V.V. Kim, N.E. Iskandarov, Z.T. Azamatov. 20th Internat. Conf on Radiation Effects in
Insulators. 19-23 August, 2019, Nur_Sultan Kazakhstan, Book of Abstract, p.161.
