Typical SEM image of molybdenum mirror surface: (a) untreated mirror surface; (b) treated mirror surface with multiple femtosecond pulse irradiation at fluence of ∼0.5 J/cm2 for a scan speed of 0.01mm/s and vertical scan step of 10 μm; (c) treated mirror surface after ∼1 h ultrasonic cleaning. Photographs shown in (d)–(f) are SEM images corresponding to (a)–(c), respectively, recorded under higher magnification. The laser polarization orientation is perpendicular to the observed LIPSSs and is parallel to the scan direction.
Typical SEM image of treated mirror surface at pulse fluence of ∼0.5 J/cm2 and scan speed of 0.01 mm/s with different vertical scan step of: 10 μm (top-left); 20 μm (top-right); 30 μm (bottom-left); and 50 μm (bottom-right). The bottom-right image is under smaller magnification to depict a raster scan.
Typical SEM image of treated molybdenum mirror surface at single pulse energy fluence of ∼0.5 J/cm2 during horizontal scanning at scan speed of 0.01 mm/s with different orientation of linear polarizations: horizontal polarization (top-left); vertical polarization (top-right); linear polarization oriented at +45o (bottom-left); and linear polarization oriented at –45o (bottom-right). This illustrates that formation of LIPSSs is always perpendicular to the linear polarization and efficiency of LIPSS formation is independent of scan direction relative to the scan direction.
Typical SEM image of molybdenum mirror surface treated with 50 linearly polarized laser pulses at single spot at ∼0.5 J/cm2 with different orientations: horizontal polarization (top-left); vertical polarization (top-right); linear polarization oriented at +45o (bottom-left); linear polarization oriented at –45o (bottom-right).
Typical SEM image of molybdenum mirror surface obtained for single and multiple laser pulses exposure at single spot position at ∼0.5 J/cm2: single pulse (top-left); 10 pulses (top-right); 100 pulses (bottom-left); 200 pulses (bottom-right).
EDS spectra of the untreated surface (left) and the treated surface (right) corresponding to molybdenum mirror surfaces shown in the Fig. 1.
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