The significant role of plasmonic effects in femtosecond laser‐induced grating fabrication on the nanoscale

Abstract

Nowadays, plasmonics aiming at manipulating light beyond the diffraction limit has aroused great interest on account of the promise of nanoscale optical devices. Generally, the ability to break diffraction barrier is achieved via controlling surface plasmons (SPs) on artificial structures as products of human ingenuity. Here, nevertheless, it is demonstrated that in short-pulse laser ablation ultrafast active plasmonic structures spontaneously generate by virtue of plasmonic effects rather than human will. First, with the experimental results on ZnO, Si, and GaAs, explicit evidence is provided for the grating-splitting phenomenon that acts as a direct route for the formation of laser-induced deep-subwavelength gratings. The splitting mechanism can break through the diffraction limit and push laser-induced structures towards the nanoscale. Then, through comprehensive numerical studies based on the viewpoint of plasmonics, we confirm that the gratingsplitting phenomenon originates in the conversion of SP modes from the resonant to the nonresonant mode and further to the inphase or antiphase asymmetric mode. In short, plasmonic effects play an important role in ultrafast laser-induced grating splitting towards the nanoscale, which will provide new insights into the mechanisms of ultrafast laser-induced nanostructures.

Surface structures induced by ultrashort laser pulses: Formation mechanisms of ripples and grooves

“…This theory is extended to excited states of the target material typically occurring in silicon irradiated by intense fs laser pulses by considering the dielectric permittivity of the excited surface [3,14]. In fact, silicon irradiated by ultrafast laser pulses tends to exhibit metallic behavior with high temperature and high free-carrier number density, which can reach values as high as 10 22 cm -3 [29].…”

“…The pioneering explanation of Sipe et al describes ripples formation as a result of inhomogeneous energy deposition, due to the interference between the incident beam and a scattered interface field [21], which eventually leads to the periodic surface modification. More recently, Tsibidis et al used hydrodynamics-based theory to explain the narrowing effect of LSFL [22], and Huang et al used rigorous coupled wave analysis and finite-difference time-domain (FDTD) methods to simulate the grating splitting phenomenon of LSFL [3]. The theory of exploding plasma nanospheres simulated by FDTD was also applied to interpret HSFL on surfaces of (semi-)transparent materials [23].…”

“…In the field of direct femtosecond (fs) laser surface micro/nano-structuring, the generation of quasi-periodic surface ripples is one of the most striking features and is gaining increasing interest [1][2][3][4]. The formation of periodic structures is boundary-less in terms of materials (metals, semiconductors and dielectrics) and has already shown perspective applications in different fields, like permanent surface color modification of metals and semiconductors [1,5], biomimetic structures with super-hydrophobic character [6][7][8], blackening of metals or silicon [9,10], solar cells [11,12] and so forth.…”

Laser-induced periodic surface structures on titanium upon single- and two-color femtosecond double-pulse irradiation

“…It is generally accepted that the LSFL originate from interference of the incident radiation with a surface electromagnetic wave (SEW), generated at the rough laser ablated surface. For strong absorbing materials (metals and semiconductors) this may include the excitation of Surface Plasmon Polaritons (SPPs) [14][15][16]. The origin of the HSFL is currently not fully understood and controversially debated in the literature [7,8,11,12,17].…”

Periodic surface structure creation by UV femtosecond pulses on silicon

“…Ultrashort laser pulses are especially promising for micromachining of various materials, since high energy density can be transferred to the materials in such a short timeframe, that thermal effects on the material are minimal. Femtosecond laser nano-and microstructuring has been investigated for the past decade [5][6][7][8][9]. The formation of laser-induced periodic surface structures (LIPSS) on silicon and on other materials is extensively investigated both theoretically and experimentally [10][11][12][13][14][15][16][17].…”