Modification Of Emission Within All-dielectric Nanoparticles And Femtosecond Laser Assisted Fabrication

High-index dielectric nanostructures have emerged as an exceptional platform of resonant nanophotonics.In virtue of low optical losses and capability to support Mie resonances especially strong magnetic multipoles,dielectric nanostructures can be employed to realize enhancement of both electric and magnetic near-fields,and modification of emitting far-fields.There are at least two branches requiring for deep research.The first one comes with comprehension of interaction between electromagnetic waves and nanostructures,and the second one optional techniques of nanofabrication.Here,starting with Mie theory,we research the impact of magnetic multipolar modes on both nearfields and scattering spectra.Then Mie resonances are applied into photoluminescence enhancement of perovskite nanoparticles.The relationship between Purcell effect and radiative lifetime of photo-induced carriers are discussed as well.Furthermore,we investigate directional emission governed by interference of electric and magnetic multipolar modes.As for nanofabrication,we prepare nanoparticles with different sizes via laser induced transfer,and explore manufacturing of nanoantenna array based on femtosecond laser direct writing.These studies are of significant values for developing dielectric nanophotonic devices.The main work is depicted as following:(1)Calculation models of Mie theory are coded via MATLAB.Taking silicon nanoparticles as examples,our results reveal domination of optical scattering by magnetic multipoles,including forming of magnetic dipoles,roles of refractive index and size parameters.Besides,multipolar scattering of non-spherical particles is also calculated by multipolar expansion method of scattering current density.(2)Halide perovskite nanoparticles are prepared using LIFT.Then the PL and radiative lifetime maps are measured.We calculate the total radiated power within the nanoparticles contributed by both electric and magnetic multipoles,and thus the Purcell factor.Considering the full PL spectrum,we obtain 5-fold enhancement of emission,which coincides with evidence from experiments.Moreover,we propose the idea for the first time that acceleration of radiative lifetimes in the nanoparticles can probably improve phase stability of hybrid halide perovskite.This size-related effect may provide the way to steady bandgap engineering of halide perovskite.(3)Directional emission induced by interference of electric and magnetic multipolar modes in the far field is studied.We seek out the best ratio of forward to backward scattering by implementing size-sweeping numerical simulations of Si3N4 nanocylinders.With respect to fabrication process,we attempt to create dielectric nanoantenna array by means of liftoff assisted by laser direct writing.Our substantive progress has shown its potential as an option of rapid fabrication of nanophotonic devices.We also design and build the forward imaging optical system for further research on directional nonlinear emission of nanoantennas.