Surface patterning on periodicity of femtosecond laser-induced ripples

Abstract

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Creation of periodic subwavelength ripples on tungsten surface by ultra-short laser pulses

“…7 Comparison of the measured data (solid squares) with the simulated results (solid curves) of the ripple period as a function of the laser fluence for the pulse width of 50 fs (a), and of the pulse width for the laser fluence of 1.5 J/cm 2 (b) SPP wavelength λ spp will be reduced. Some previous studies have already proved that the surface roughness is ready to increase with larger overlapped pulse numbers N [25,29]. If f (N, v s ) is defined as an increasing function of the surface roughness related to the scanning speed or the overlapped pulse numbers, we can easily obtain a relationship of λ spp = λ spp /f (N, v s ).…”

“…Compared with the long time duration of laser pulses, femtosecond laser-induced ripples usually have the following distinct characteristics: (i) even at the normal angle of incidence, the periodic ripple spacing can be much less than the incident laser wavelength (0.1-0.75λ laser ) [8,14,18,22]; (ii) the ripple period increases with higher laser fluences but decreases with greater cumulative pulse numbers [9,13,20,23]; (iii) both the threshold laser fluence and the available ripple period depend on the surface roughness [17,18,24,25]. Besides the classical interpretation of the optical interference, several other possible mechanisms have also been suggested by some authors [21,26,27], but none of them could sufficiently account for the abovementioned ripple features, and how to deeply understand the ripple formation by ultra-short laser pulses is still elusive, especially for the metallic materials.…”

Optical properties of the Ti surface structured by femtosecond laser beam

“…They pointed that formation of laser-induced RAP occurs in materials with the real part of dielectric permittivity situated within the region -1<ε<1. These values of ε can be obtained in the plasma escaped from the metal surface under action of femtosecond laser pulses [22]. It is this jump in dielectric permittivity from metallic to the dielectric type that can provoke formation of RAP and the following chemical transformation of surface from metallic to dielectric compound.…”

Induced hydrophobicity in micro‐ and nanostructured nickel thin films obtained by ultraviolet pulsed laser treatment

“…The use of a 50 µm mask would therefore create the features observed experimentally, with 50 µm-period higher walls in parallel to the scanning direction and smaller periodic lines in perpendicular. These latter features arise as a consequence of 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 the 5 µm rastering laser step and are not to be confused with laser induced ripples, which are sub-wavelength structures that form as a result of laser interference [48][49][50][51].…”