ИСТИНА

Chalcogenide vitreous semiconductors (ChVS) are of great interest for infrared photonics and optical storage media due to high transmittance in the near-infrared (IR) range, reversible phase transitions and possibility of submicron femtosecond laser-induced periodic surface structures (LIPSS) formation in these materials. In the latter case, high-contrast periodic surface relief can cause optical anisotropy, which is promising for polarization-sensitive optics. Therefore, our study was aimed to produce various LIPSS types on the ChVS films and analyze their structural and optical properties. We used As2Se3 films (850 ± 5 nm thickness) on glass and chromium substrates. Various LIPSS types were formed by femtosecond laser pulses (515 nm, 300 fs, pulses fluence and number E = 30 – 270 mJ/cm2, N = 10–1200) on the film surfaces, with both subwavelength (160±10 nm) and wavelength (480±10 nm) periods, and ridges formed parallel or perpendicular to the laser polarization, respectively. With fluence and/or pulses number increase, the type of LIPSS changes from subwavelength to wavelength ones. During such transition, gratings of both types can be formed simultaneously within the same crater as hierarchical structure. Reflection and transmission IR spectra analysis in polarized light showed the presence of birefringence in the irradiated areas containing LIPSS. The difference between the refractive indices of ordinary and extraordinary waves, determined from the interference maxima positions in the IR spectra, amounted up to 0.1. Additionally, Raman spectra analysis indicated possible laser-induced phase transitions in As2Se3. The work was supported by Russian Science Foundation (grant 22-19-00035)