A study of high-NA focusing process of ultrashort laser pulses in bulk of ZnSe has been carried out. It is shown that when focusing laser Gaussian beam with high-aperture lenses into a transparent medium aberration distortions occur leading to an increase in focal spot size. The results of experimental studies on ablation of front and back surfaces of a plane-parallel plate with 4 mm thickness made of ZnSe by laser pulses with a duration of 0.3 ps, 1 ps, 10 ps and a wavelength of 1030 nm focused by a micro lens (NA=0.55) are presented. It is shown that at low pulse energies focusing can be considered in a linear mode in which focal spot size is due to aberration distortions. Keywords: direct laser writing, femtosecond laser pulses, high-NA focusing, ablation, aberrations.
In this work, we study the nonlinear absorption of ultrashort laser pulses of variable duration (0.3-10 ps) in a bulk polycrystalline ZnSe dielectric. The transmission of the sample was measured for two wavelengths, 515 and 1030 nm, in a wide range of intensities. A nonlinear behavior of the transmission is found when the sample is irradiated with laser radiation at a wavelength of 515 nm with absorption saturation in the region of 3-5 TW/cm2. Surface damage thresholds were obtained for a wavelength of 1030 nm for pulse durations of 0.3-10 ps. Keywords: nonlinear ZnSe absorption, solid-state immersion, two-photon absorption, chalcogenide glass surface ablation, ZnSe ablation thresholds.
The silicon surface was modified in a single-pulse mode with femto-picosecond laser pulses (0.3 and 10 ps) in the near-IR range (1030 nm) during ablation in air and water. The resulting structures were studied using Raman microscopy. In the course of the study, it was found that nanocrystallites with a size of 7-8 nm appear at the crater boundary. Local mechanical stresses were found in the center of the crater, the sign of which depends on the applied energy density. The highest local compressive stresses arise in water in the subfilamentation mode at maximum energy densities. Keywords: silicon, Raman spectroscopy, ultrashort pulses, single-pulse ablation in air and liquid, local stresses.
The interaction of femtosecond laser pulses with the surface of silica glass has been studied. As a result of interference between the incident radiation and surface plasmon polaritons, the formation of self-organizing subwavelength periodic structures with a period of 250 nm was observed. The minimum pulse energy at which recording occurs without surface ablation has been revealed. Keywords: direct laser recording, femtosecond laser pulses, silica, nanogratings.
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