Nanograting formation through surface plasmon fields induced by femtosecond laser pulses

Abstract

Ablation of solid surfaces irradiated with superimposed multiple shots of low fluence femtosecond (fs) laser pulses often results in the formation of periodic nanostructures on the target surface. We demonstrate that the self-organization process of nanostructuring can be regulated to fabricate a homogeneous nanograting on the target surface in air. A simple two-step ablation process was used to control the nanoscale energy deposition that should be developed through the excitation of surface plasmon polaritons (SPPs) during the fs laser-surface interaction. The results obtained for crystalline gallium nitride represent exactly the nature of a single spatial standing wave mode of SPPs of which periodically enhanced near-fields ablate the target surface to form the nanograting with a period of ∼200 nm. The calculated results for a model target reproduce well the observed nanograting period and explain the origin of its characteristic properties.

Nanograting formation on metals in air with interfering femtosecond laser pulses

“…9,10 Under this condition, we have shown that a flat target surface is nanostructured through bonding structure change of the material, [11][12][13] near-field ablation around the corrugated nanosurface, [13][14][15] and excitation of standing surface plasmon polariton (SPP) waves. [15][16][17] These interaction processes could explain the origin and growth of PNSs on DLC, 15 Si, 16 and GaN, 17 where the theoretical calculation reproduced well the observed nanoperiod much smaller than $k/2. Based on the mechanism, we developed a two-step ablation technique to control the interaction and imprint a homogeneous nanograting in air.…”

“…Based on the mechanism, we developed a two-step ablation technique to control the interaction and imprint a homogeneous nanograting in air. 17 In contrast, only a few kinds of metals are known of which surfaces have been periodically nanostructured through the fs-laser ablation in air. Stainless steel (SUS) [18][19][20] and Ti 7,21-24 are the most common metals structured at the groove period smaller than $k/2, while the PNS formation was observed for Cu, 25,26 Al, 27 and W 28 under the specific conditions.…”

“…In addition, the grating period d $ K/q given by a single integer q ensures the excitation of a single spatial standing SPP wave mode, as discussed in detail in our recent study. 17 The SPP waves propagating in opposite directions on the fringe can induce the line-like ablation even at the midway of two adjacent fringes.…”

Laser printed nano-gratings: orientation and period peculiarities

“…The SPP wave between dielectric (glass) and plasma can be launched when Re( ε p ) ≤ − n 2 , where ε p is the permittivity of plasma at the focal volume (a necessary condition with the Bragg phase-matching being the satisfactory condition)1131323334. This follows from the requirement of the wave vector of the surface wave to be a real number, where k 0  = 2 π / λ .…”

Cell spreading on titanium periodic nanostructures with periods of 200, 300 and 600 nm produced by femtosecond laser irradiation

“…Periodic nanostructures can be created with femtosecond lasers on metals [6][7][8][9][10], semiconductors [11][12][13][14][15][16][17][18][19] and also inside transparent materials [20]. The periodic nanostructures are self-organized in the laserfocused spot, and their arrangement depends on the laser wavelength.…”