Assembling of Silicon Nanoflowers with Significantly Enhanced Second Harmonic Generation Using Silicon Nanospheres Fabricated by Femtosecond Laser Ablation

Abstract

Silicon (Si) nanospheres (NSs) with diameters ranging from about 10 to 100 nm were fabricated by using femtosecond (fs) laser ablation of a silicon wafer immersed in deionized water. Si nanoflowers (NFs) looking like snowflakes were assembled by dropping and drying the colloid solution on a glass slide. Transmission electron microscope observation revealed that Si NFs were composed of self-assembled Si NSs with different sizes. The nonlinear optical responses of both single Si NSs and Si NFs were examined by using a focused fs laser at ∼800 nm. While only second harmonic generation (SHG) with weak intensity was observed for single Si NSs, a significant enhancement in SHG was found for Si NFs. More interestingly, both the Stokes and anti-Stokes components of the Raman scattering of the SH were also revealed in the nonlinear response spectra of Si NFs, possibly due to the large enhancement in SHG. The electric field distributions were numerically simulated by using the finite-difference time-domain technique for single Si NSs and corresponding aggregates composed of seven closely packed NSs at the wavelengths of both the fundamental light and the SH. It was revealed that the significant enhancement in electric field achieved in the aggregates of Si NSs is responsible for the strong SHG observed in Si NFs.

Laser printing of silicon nanoparticles with resonant optical electric and magnetic responses

“…Unique optical properties of silicon nanoparticles cannot be exploited and used without a simple method for their controlled fabrication. Chemical methods 10,21,22 , plasma synthesis 23 and laser ablation in air or liquids 17,24,25 can produce silicon nanoparticles with sizes in a broad range (from nm to mm), but without possibilities of the required size control and precise deposition of these nanoparticles. Lithographic methods 26 are more complex and do not allow the fabrication of spherical nanoparticles.…”

Large-Scale and Low-Cost Fabrication of Silicon Mie Resonators

“…Indeed, excitation of Mie resonances in such nanoparticles results in strong light scattering and an optical near-field enhancement, along with low Ohmic losses and thermal stability. However, silicon nanoparticles show multiple magnetic and electric resonances in the visible and the near-infrared spectral regions. − Then the overlap between their electric and magnetic resonance modes provides Mie resonators unique light scattering properties like Kerker-type high directional scattering. , All these optical properties allow silicon nanoparticles to be used in many applications like nonlinear optics, − Raman scattering enhancement, directional optical sorting, color printing, − ultrafast optical switching, wavefront manipulation, optical heating (with submicronic particles), and many others.…”

Optical Scattering of Liquid Gallium Nanoparticles Coupled to Thin Metal Films

“…Ga NPs with different diameters ranging from 150 to 650 nm were fabricated by using femtosecond (fs) laser ablation. A focused fs laser light (Legend, Coherent) with a pulse duration of 100 fs and a repetition rate of 1 kHz was employed to ablate a Ga film in air and the Ga NPs ejected from the Ga film were collected by using a metal/SiO substrate, as illustrated in Figure 1 a [ 52 ]. Such spherical Ga NPs exhibited a core-shell structure with a liquid Ga core and a gallium trioxid (Ga O ) shell [ 32 ].…”