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Femtosecond laser-induced periodic surface structures (LIPSS) have several applications in surface structuring and functionalization. Three major challenges exist in the fabrication of regular and uniform LIPSS: enhancing the periodic energy deposition, reducing the residual heat, and avoiding the deposited debris. Herein, we fabricate an extremely regular low-spatial-frequency LIPSS (LSFL) on a silicon surface by a temporally shaped femtosecond laser. Based on a 4 f configuration zero-dispersion pulse shaping system, a Fourier transform limit (FTL) pulse is shaped into a pulse train with varying intervals in the range of 0.25–16.2 ps using periodic π -phase step modulation. Under the irradiation of the shaped pulse with an interval of 16.2 ps, extremely regular LSFLs are efficiently fabricated on silicon. The scan velocity for fabricating regular LSFL is 2.3 times faster, while the LSFL depth is 2 times deeper, and the diffraction efficiency is 3 times higher than those of LSFL using the FTL pulse. The formation mechanisms of regular LSFL have been studied experimentally and theoretically. The results show that the temporally shaped pulse enhances the excitation of surface plasmon polaritons and the periodic energy deposition while reducing the residual thermal effects and avoiding the deposition of the ejected debris, eventually resulting in regular and deeper LSFL on the silicon surface.

Over the past two decades, femtosecond laser-induced periodic structures (femtosecond-LIPSs) have become ubiquitous in a variety of materials, including metals, semiconductors, dielectrics, and polymers. Femtosecond-LIPSs have become a useful laser processing method, with broad prospects in adjusting material properties such as structural color, data storage, light absorption, and luminescence. This review discusses the formation mechanism of LIPSs, specifically the LIPS formation processes based on the pump-probe imaging method. The pulse shaping of a femtosecond laser in terms of the time/frequency, polarization, and spatial distribution is an efficient method for fabricating high-quality LIPSs. Various LIPS applications are also briefly introduced. The last part of this paper discusses the LIPS formation mechanism, as well as the high-efficiency and high-quality processing of LIPSs using shaped ultrafast lasers and their applications.

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By using infrared to ultraviolet (IR-UV) femtosecond laser directing, periodic nanostructures were efficiently fabricated on an F-doped tin oxide (FTO) film with a thickness of 650 nm. The morphology of the nanostructures and duty cycle were studied in detail by changing the laser fluence and scanning speed, where three lasers with central wavelengths of 343, 515, and 1,030 nm were used in the experiments. Under the 515 nm laser irradiation with scanning speed of 0.01 mm/s and laser fluence of 23 mJ/cm2, the periods Λ is 172 nm, the ablated nanogroove with width w2 is 52 nm, the birefringence Δn reached a maximum of 0.21, and the phase retardance was up to 135 nm. The morphology of the nanostructures and the birefringence effects of the FTO film prepared by a femtosecond laser at wavelengths of 1,030 and 343 nm were also studied, where the phase retardance of the nanostructured FTO film was much lesser than for the 515 nm laser because the thickness of the nanoripples layer, and, thus, the duty cycle of periodic nanoripples was smaller. Finally, a large-area FTO film with periodic nanostructures was fabricated efficiently by direct laser writing using a 515 nm fs laser beam focused via a cylindrical lens, and demonstrated the characteristics of a quarter-wave plate for 532 nm light.