Engineering Atypical Multidimensional Periodic Surface Nanostructures on ZnO via Femtosecond Laser for Efficient Optical Diffraction and Structural Coloring

Conventional laser-induced periodic surface microstructures (LIPSSs) exhibit one-dimensional features with spatial periods of the near-subwavelength scale and a polarization-dependent orientation. In this work, we demonstrate the simultaneous formation of multidimensional and atypical periodic nanostructures on crystalline zinc oxide (ZnO) through the femtosecond laser-induced periodic surface nanostructure (FsLIPSS) using two kinds of femtosecond laser wavelengths (1030 nm, 150 fs, 1 kHz and 800 nm, 35 fs, 666 Hz). Traditional FsLIPSSs with polarization-controlled orientation have been observed, while an atypical FsLIPSS independent of polarization and a distinct two-dimensional (2D) irregular LIPSS are generated with a single femtosecond laser. These atypical LIPSSs with a tilt angle of nearly 23° can be obtained for both wavelengths within specific laser power and scanning speed ranges. In the meantime, 2D FsLIPSSs are further identified under specific laser polarization direction and scanning speed. This phenomenon can be attributed to the laser pulse overlay-induced interference effect. Furthermore, the structural coloring and optical diffraction performance of traditional and atypical FsLIPSSs as diffraction grating devices are also demonstrated, showcasing a more pronounced diffraction effect and superior structural coloring, which can be expected to be applied in ZnO-based diffraction optical devices and miniaturized spectroscopic systems.