ИСТИНА

Chalcogenide vitreous semiconductors (ChVSs) are applied as a basis of the rewritable optical memory [1] and infrared photonic devices due to the possibility of fast and reversible phase transitions, as well as high refractive index and transmission in the near- and mid-infrared spectral range [2]. Laser-induced periodic surface structures (LIPSS) formation on such materials provides prospects for increasing information storage capacity and create polarization-sensitive optical elements of infrared photonics. LIPSS formation accompanied by laser-induced phase transitions currently is well studied for Ge2Sb2Te5 films [4], however for infrared photonic applications, arsenic sulfide (As2S3) and arsenic selenide (As2Se3) seem to be more promising materials [5]. In presented work, thin As2S3 and As2Se3 films (576 ± 5 nm and 842 ± 5 nm, respectively) deposited on single-crystal silicon substrates with a chromium sublayer (100 nm) or on quartz glasses were irradiated with femtosecond laser pulses (300 fs) at the second optical harmonic frequency (515 nm) using Satsuma laser system (energy and number of pulses E = 0.1–0.4 μJ, N = 10–1200) at normal incidence. As a result of femtosecond laser irradiation, LIPSS were formed on the surface of the films in the form of one-dimensional gratings with wavelength (~515 nm) and subwavelength (150–185 nm) periods, oriented, respectively, orthogonally or along the polarization vector. The period and orientation of LIPSS varied depending on the number and energy of laser pulses and was consistent with the results of numerical simulation within the framework of the plasmon-polariton mechanism for the formation of these structures. It also was shown experimentally and confirmed by numerical simulation that both wavelength and subwavelength structures can be observed simultaneously within the same crater formed by a femtosecond laser impact, in the form of a hierarchical structure of two orthogonal gratings with different periods. Additionally, a possibility to produce large areas (5x5 mm2) covered by hierarchical LIPSS using femtosecond laser raster scanning was demonstrated. Raman spectra analysis (Horiba HR800, 488 nm excitation) demonstrated no structural changes in As2S3 films. However, femtosecond laser-induced phase transformations are possible for As2Se3 films according to Raman data. The work was supported by Russian Science Foundation (project 22-19-00035). REFERENCES: [1] P. Guo, A.M. Sarangan and I. Agha, Appl. Sci. 9, 530 (2019) [2] J.S. Sanghera, L.B. Shaw, et al., Fiber Integr. Opt. 19, 251–274 (2000) [3] A.S. Lipatiev, S.S. Fedotov, et al., Appl. Opt. 57, 978 (2018) [4] S. Zabotnov, A. Kolchin, et al. Micro, 2, 88–99 (2022) [5] W. Ma, L. Wang, et al. Opt. Express 27, 30090–30101 (2019)