32 research outputs found
Magnetic dipole radiation tailored by substrates: numerical investigation
Nanoparticles of high refractive index materials can possess strong magnetic
polarizabilities and give rise to artificial magnetism in the optical spectral
range. While the response of individual dielectric or metal spherical particles
can be described analytically via multipole decomposition in the Mie series,
the influence of substrates, in many cases present in experimental
observations, requires different approaches. Here, the comprehensive numerical
studies of the influence of a substrate on the spectral response of high- index
dielectric nanoparticles were performed. In particular, glass, perfect electric
conductor, gold, and hyperbolic metamaterial substrates were investigated.
Optical properties of nanoparticles were characterized via scattering
cross-section spectra, electric field profiles, and induced electric and
magnetic moments. The presence of substrates was shown to introduce significant
impact on particle's magnetic resonances and resonant scattering
cross-sections. Variation of substrate material provides an additional degree
of freedom in tailoring properties of emission of magnetic multipoles,
important in many applications.Comment: 10 page, 28 figure
Probing and control of guided exciton-polaritons in a 2D semiconductor-integrated slab waveguide
Guided 2D exciton-polaritons, resulting from the strong coupling of excitons
in semiconductors with non-radiating waveguide modes, provide an attractive
approach towards developing novel on-chip optical devices. These quasiparticles
are characterized by long propagation distances and efficient nonlinear
interaction but cannot be directly accessed from the free space. Here we
demonstrate a powerful approach for probing and manipulating guided polaritons
in a Ta2O5 slab integrated with a WS2 monolayer using evanescent coupling
through a high-index solid immersion lens. Tuning the nanoscale lens-sample gap
allows for extracting all the intrinsic parameters of the system. We also
demonstrate the transition from weak to strong coupling accompanied by the
onset of the motional narrowing effect: with the increase of exciton-photon
coupling strength, the inhomogeneous contribution to polariton linewidth,
inherited from the exciton resonance, becomes fully lifted. Our results enable
the development of integrated optics employing room-temperature
exciton-polaritons in 2D semiconductor-based structures
Probing magnetic and electric optical responses of silicon nanoparticles
We study experimentally both magnetic and electric optically induced resonances of silicon nanoparticles by combining polarization-resolved dark-field spectroscopy and near-field scanning optical microscopy measurements. We reveal that the scattering spectra exhibit strong sensitivity of electric dipole response to the probing beam polarization and attribute the characteristic asymmetry of measured near-field patterns to the excitation of a magnetic dipole mode. The proposed experimental approach can serve as a powerful tool for the study of photonic nanostructures possessing both electric and magnetic optical responses.This work was financially supported by Government of
Russian Federation (Project Nos. 14.584.21.0009 10 and
GOSZADANIE 2014/190, Zadanie No. 3.561.2014/K, 074-
U01), Russian Foundation for Basic Research and the
Australian Research Council