Multiscale Hierarchical Micro/Nanostructures Created by Femtosecond Laser Ablation in Liquids for Polarization-Dependent Broadband Antireflection

Abstract

In this work, we present the possibility of producing multiscale hierarchical micro/nanostructures by the femtosecond laser ablation of transition metals (i.e., Ta and W) in water and investigate their polarization-dependent reflectance. The hierarchical micro/nanostructures are composed of microscale-grooved, mountain-like and pit-rich structures decorated with hybrid laser-induced periodic surface structures (LIPSSs). The hybrid LIPSSs consist of low/high and ultrahigh spatial frequency LIPSSs (LSFLs/HSFLs and UHSFLs). LSFLs/HSFLs of 400–600 nm in a period are typically oriented perpendicular to the direction of the laser polarization, while UHSFLs (widths: 10–20 nm and periods: 30–50 nm) are oriented perpendicular to the curvatures of LSFLs/HSFLs. On the microstructures with height gradients, the orientations of LSFLs/HSFLs are misaligned by 18°. On the ablated W metasurface, two kinds of UHSFLs are observed. UHSFLs become parallel nanowires in the deep troughs of LSFLs/HSFLs but result in being very chaotic in shallow LSFLs, turning into polygonal nanonetworks. In contrast, chaotic USFLs are not found on the ablated Ta metasurfaces. With the help of Fourier transform infrared spectroscopy, it is found that microgrooves show an obvious polarization-dependent reflectance at wavelengths of 15 and 17.5 μm associated with the direction of the groove, and the integration of microstructures with LSFs/HSFLs/UHSFLs is thus beneficial for enhancing the light absorbance and light trapping in the near-to-mid-infrared (NIR-MIR) range.

Water Decomposition Occurring During Laser Breakdown of Aqueous Solutions Containing Individual Gold, Zirconium, Molybdenum, Iron or Nickel Nanoparticles

“…Nowadays, the optical breakdown of liquids is intensively studied [1][2][3]. This topic is mainly associated with laser ablation technologies in liquids [4][5][6] and Laser-Induced Breakdown Spectroscopy (LIBS) technology [7][8][9].…”

Modeling Electromagnetic Nanostructures and Experimenting With Nanoelectric Elements to Form Periodic Structures

“…The modelingbased results may then be compared with those of the experiments to determine the overall match. This classic approach to numerical model creation has been widely employed [2,6,11,14,15,18,21,25,29,33,35,36,42,47,51,52], as also shown through the relevant criterion (1) ad A). To perform the associated qualitative analysis, it is convenient to use the classification embodied in the above precondition (1), ad B), which covers the behavior of the dynamic system inside the modeled structure; for cases of strong coupling between the internal and the external electromagnetic fields, some basic aspects of the modeled object are comprised, too.…”

Modeling and Experimental Verification of Plasma Jet Electromagnetic Signals

“…One of the diagnostic approaches is embodied in the analysis of radio frequency (RF) electromagnetic signals, a procedure often utilized in tasks such as the diagnostics of microplasma [5][6][7][8], which generates high-frequency (HF) signals characterized by specific spectra. The actual discharge creates a compound signal [5][6][7][8] capable of being theoretically described and modeled [11][12][13][14][15][16][17][18][19][20]. To verify the functionality of the method, we employed an atmospheric-pressure plasma source, namely, a plasma pencil (Figure 1) similar to that modeled in report [11].…”