  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.
