Coherent scatter-controlled phase-change grating structures in silicon using femtosecond laser pulses

Abstract

Periodic structures of alternating amorphous-crystalline fringes have been fabricated in silicon using repetitive femtosecond laser exposure (800 nm wavelength and 120 fs duration). The method is based on the interference of the incident laser light with far- and near-field scattered light, leading to local melting at the interference maxima, as demonstrated by femtosecond microscopy. Exploiting this strategy, lines of highly regular amorphous fringes can be written. The fringes have been characterized in detail using optical microscopy combined modelling, which enables a determination of the three-dimensional shape of individual fringes. 2D micro-Raman spectroscopy reveals that the space between amorphous fringes remains crystalline. We demonstrate that the fringe period can be tuned over a range of 410 nm – 13 µm by changing the angle of incidence and inverting the beam scan direction. Fine control over the lateral dimensions, thickness, surface depression and optical contrast of the fringes is obtained via adjustment of pulse number, fluence and spot size. Large-area, highly homogeneous gratings composed of amorphous fringes with micrometer width and millimeter length can readily be fabricated. The here presented fabrication technique is expected to have applications in the fields of optics, nanoelectronics, and mechatronics and should be applicable to other materials.

Analysis of nascent silicon phase-change gratings induced by femtosecond laser irradiation in vacuum

“…It is worth noticing that the formation of periodic patterns of amorphous and crystalline regions was recently reported during few pulses fs laser irradiation of p-doped (100) silicon 17 . Moreover, extension of this fringe pattern over larger areas and period tuning by appropriate selection of the experimental conditions have also been recently demonstrated 18 , 19 . Differently from the present investigation, in the previous cases the fringe pattern forms in air at the center of the irradiation spot in sub-ablative experimental conditions.…”

Surface Plasmon Polaritons on Rough Metal Surfaces: Role in the Formation of Laser-Induced Periodic Surface Structures

“…Despite the importance of , there are surprisingly few works on systematic studies of this parameter, and these works are limited to a very narrow selection of materials. 2,[22][23][24][25] For the specific case of metals, the wave propagating at the surface that contributes to ripple formation is generally identified as a surface plasmon polariton [26][27][28][29] coupled in from the incident light with help from a non-negligible surface roughness. The role of surface roughness is thus to impart momentum to the incident wave, bridging the momentum mismatch between the parallel component of the wavevector of such incident wave with that of the SPP, which lies beyond the light cone.…”

Surface Plasmon Polariton Triggered Generation of 1D-Low Spatial Frequency LIPSS on Fused Silica

“…While the majority of scientific studies of LSFL on dielectric materials are based on punctual structures [12,15,27,28], i.e., LSFL are generated on a single spot only, for industrial applications, the generation of one-and two-dimensional LSFL is mandatory by scanning the laser. For metals [1][2][3][4]14,29,30] and semiconductors [5,[31][32][33], this has been shown in several publications because of the convenience in generating LSFL on these materials with free charged carriers ( < 0). For dielectric materials, e.g., fused silica, the authors recently have shown the transfer from punctual laser irradiation into the dynamic range, i.e., moving the laser spot over the sample [16].…”