We unraveled a novel optical bistable state in amorphous silicon nanocuboids, featuring an abrupt super-linear jump of scattering intensity during hysteretic switching. The effective intensity dependency reaches 19th power, leading to an nonlinear index n2 as large as 5 μm2/mW, 7-order larger than the bulk value and well explained through coupled electromagnetic and photothermal simulation. Combining the ultralarge super-linear response with dark-field laser scanning microscopy, 3.5-times resolution enhancement was achieved, without any need of temporal/spatial excitation modulation. This hysteresis scattering not only sets a benchmark in optical super-resolution technique, but also suggests further optical signal processing potentials.
In contrast to paraxial waves, strongly confined light can carry significant transverse spin angular momentum. Here we
report on its direct detection in the evanescent electromagnetic field near the ultrathin waist of an optical nanofiber
waveguide. We demonstrate the spin by its contribution to rotation of an anisotropic microsphere held and spun near the
nanofiber waist by optical tweezers. By setting the driving spin angular momentum in the optical tweezers to be parallel
or antiparallel with respect to the transverse spin near the nanofiber, we can speed up or slow down the particle’s rotation
by about a half of the rotation rate observed without the light in the fiber. We also explore the dependence of this
optomechanical effect on the propagation direction and polarization of the guided light.
Embedding Ge-quantum dot emitters in Mie resonators leads to an enhancement of their luminescence efficiency due to the Purcell effect. To increase this effect, collective Mie resonances in extended Mie-resonator chains are investigated leading to a partial cancellation of radiation losses and experimentally observed Q-factors of up to 500. The corresponding modes and their field localization are theoretically analysed and traced back to a combination of individual oscillating dipoles.
CMOS-compatible light emitters are intensely investigated for integrated active silicon photonic circuits. One of the approaches to achieve on-chip light emitters is the epitaxial growth of Ge(Si) QDs on silicon. Their broad emission in 1.3-1.5 um range is attractive for the telecomm applications.
We investigate optical properties of Ge(Si) QD multilayers, that are grown in a thin Si slab on a SOI wafer, by steady-state and time-resolved micro-photoluminescence. We identify Auger recombination as the governing mechanism of carrier dynamics in such heterostructures.
Then we demonstrate the possibility of light manipulation at the nanoscale by resonant nanostructures investigating Si nanodisks with embedded Ge(Si) QDs. We show that the Mie resonances of the disks govern the enhancement of the photoluminescent signal from the embedded QDs due to a good spatial overlap of the emitter position with the electric field of Mie modes. Furthermore, we engineer collective Mie-resonances in a nanodisk trimer resulting in an increased Q-factor and an up to 10-fold enhancement of the luminescent signal due to the excitation of anti-symmetric magnetic and electric dipole modes.
Using time-resolved measurements we show that the minima of the radiative lifetime coincide with the positions of the Mie resonances for a large variation of disk sizes confirming the impact of the Purcell effect on QD emission rate. Purcell factors at the different Mie-resonances are determined.
CMOS-compatible light emitters are intensely investigated for integrated active silicon photonic circuits. One of the approaches to achieve on-chip light emitters is the epitaxial growth of Ge(Si) QDs on silicon. Their broad emission in the 1.3-1.5 um range is attractive for the telecom applications.
We investigate optical properties of Ge(Si) QD multilayers, which are grown in a thin Si slab on an SOI wafer, by steady-state and time-resolved micro-photoluminescence. We identify Auger recombination as the governing mechanism of carrier dynamics in such heterostructures.
Then we demonstrate the possibility of light manipulation at the nanoscale by resonant nanostructures investigating Si nanodisks with embedded Ge(Si) QDs. We show that the Mie resonances of the disks govern the enhancement of the photoluminescent signal from the embedded QDs due to a good spatial overlap of the emitter position with the electric field of Mie modes. Furthermore, we engineer collective Mie-resonances in a nanodisk trimer resulting in an increased Q-factor and an up to 10-fold enhancement of the luminescent signal due to the excitation of anti-symmetric magnetic and electric dipole modes.
Using time-resolved measurements we show that the minima of the radiative lifetime coincide with the positions of the Mie resonances for a large variation of disk sizes confirming the impact of the Purcell effect on QD emission rate. Purcell factors at the different Mie-resonances are determined.
In this presentation we will discuss the analytical and numerical approaches to modeling electromagnetic properties of geometrically regular subwavelength 2D arrays of random resonant plasmonic particles.
Amorphous metamaterials and metasurfaces attract interest of the scientific community due to promising technological implementations with cost-efficient methods of large-scale chemical nanoparticles synthesis as well as their self-organization. Random fluctuations of the particles size, shape, and/or composition are inevitable not only in the bottom-up synthesis, but also in conventional electron beam and photolithography fabrication. Despite the significant progress in large-scale fabrication, modeling and effective properties prediction of random/amorphous metamaterials and metasurfaces is still a challenge, which we address here. We present our results on analytical modelling of metasurfaces with regular periodic arrangements of resonant nanoparticles of random polarizability/size/material at normal plane-wave incidence. We show that randomness of the polarizability is related to increase in diffused scattering and we relate this phenomenon to a modification of the dipoles’ interaction constant. As a result, we obtain a simple analytical formula which describes diffuse scattering in such amorphous metasurfaces. Employing the supercell approach we numerically confirm the analytical results.
The proposed approach can be easily extended from electrical dipole arrays and normal wave incidence to more general cases of electric and magnetic resonant particles and oblique incidence.
We review a new, rapidly developing field of all-dielectric nanophotonics which allows to control both magnetic and electric response of structured matter by engineering the Mie resonances in high-index dielectric nanoparticles. We discuss optical properties of such dielectric nanoparticles, methods of their fabrication, and also recent advances in all-dielectric metadevices including couple-resonator dielectric waveguides, nanoantennas, and metasurfaces.
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