2 research outputs found
Resonant Chiral Effects in Nonlinear Dielectric Metasurfaces
We
study the resonant enhancement of linear and nonlinear chiroptical
effects in planar silicon metasurfaces with an in-plane asymmetry
supporting multipolar Mie resonances and quasi-bound states in the
continuum (quasi-BICs). We demonstrate theoretically and observe in
experiment the pronounced linear circular dichroism at the quasi-BIC resonances originating from the interaction of
modes with the substrate. We further find that both local field enhancement
and third-harmonic signal are large for Mie resonances and some quasi-BIC
modes due to the critical coupling. We demonstrate experimentally
a strong nonlinear chiroptical response associated with high efficiency
of the third-harmonic generation and large nonlinear circular
dichroism varying from +0.918 ± 0.049 to −0.771
± 0.004 for the samples with different asymmetries. We reveal
the nonreciprocal nature of nonlinear chirality governed by the microscopic
symmetry of nonlinearities and macroscopic symmetries of the meta-atom
and metasurface lattice. We believe our results suggest a general
strategy for engineering nonlinear chiroptical response in dielectric
resonant metasurfaces
Observation of Enhanced Generation of a Fifth Harmonic from Halide Perovskite Nonlocal Metasurfaces
Lead
halide perovskites are widely employed in photonic and light-emitting
devices because of their rich optoelectronic properties and simplicity
of fabrication based on low-cost flexible technologies. Perovskite
bulk crystals and films demonstrate outstanding nonlinear characteristics
with large optical nonlinearities exceeding the nonlinear susceptibilities
of conventional semiconductor materials by several orders of magnitude.
One of the promising approaches for further enhancement of the nonlinear
response of perovskites as dielectric photonic materials is to employ
optical resonances of structured surfaces, or metasurfaces. Nonlocal
metasurfaces supporting lattice modes over many unit cells provide
a new approach to both spatial and spectral control of light fields,
and they may deliver improved characteristics of nonlinear effects
for a wide range of applications associated with broadband excitation
of multiple high-quality resonances. Here we report on the first observation
of enhanced fifth harmonic generation in MAPbBr3 halide
perovskite nonlocal metasurfaces driven by high-quality resonances
at the generated harmonic wavelength in the visible frequency range.
The demonstrated enhancement is about 2 orders of magnitude compared
to an unpatterned MAPbBr3 film of the same thickness, and
is broadband by virtue of the excitation of multiple resonant modes
in the highly nonlocal regime. Our work suggests a novel approach
for achieving parametric processes in resonant dielectric structures
with high efficiency