Laser fabrication of crystalline silicon nanoresonators from an amorphous film for low-loss all-dielectric nanophotonics

TLDR

High‑index subwavelength dielectric nanoresonators support electric and magnetic resonances, promising for waveguiding, sensing, and nonlinear devices, but defects in the resonators increase internal losses and diminish their resonant performance. The study seeks to fabricate low‑loss crystalline silicon nanoresonators by starting from crystalline material. Crystalline silicon nanoparticles were produced by femtosecond laser ablation of amorphous silicon thin films using laser‑induced transfer and a novel laser‑writing technique for large‑scale fabrication. Raman spectroscopy and TEM confirm the crystallinity of the nanoparticles, and dark‑field spectroscopy and full‑wave simulations demonstrate their optical resonant properties.

Abstract

The concept of high refractive index subwavelength dielectric nanoresonators, supporting electric and magnetic optical resonances, is a promising platform for waveguiding, sensing, and nonlinear nanophotonic devices. However, high concentration of defects in the nanoresonators diminishes their resonant properties, which are crucially dependent on their internal losses. Therefore, it seems to be inevitable to use initially crystalline materials for fabrication of the nanoresonators. Here, we show that the fabrication of crystalline (low-loss) resonant silicon nanoparticles by femtosecond laser ablation of amorphous (high-loss) silicon thin films is possible. We apply two conceptually different approaches: recently proposed laser-induced transfer and a novel laser writing technique for large-scale fabrication of the crystalline nanoparticles. The crystallinity of the fabricated nanoparticles is proven by Raman spectroscopy and electron transmission microscopy, whereas optical resonant properties of the nanoparticles are studied using dark-field optical spectroscopy and full-wave electromagnetic simulations.