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
A Centimeter-Scale Dielectric Metasurface for the Generation of Cold Atoms
The
single-beam magneto-optical trap (MOT) based on the diffractive
optical element offers a new route to develop compact cold atom sources.
However, the optical efficiency in the previous single-beam MOT systems
is usually low and unbalanced, which will affect the quality of the
trapped atoms. To solve this issue, we developed a centimeter-scale
dielectric metasurface optical chip with dynamic phase distributions,
which was used to split a single incident laser beam into five separate
ones with well-defined polarization states and uniform energy distributions.
The measured diffraction efficiency of the metasurface is up to 47%.
A single-beam MOT integrated with the metasurface optical chip was
then used to trap the 87Rb atoms with numbers ∼1.4
× 108 and temperatures ∼7.0 μK. The proposed
concept in this work may provide a promising solution for developing
ultracompact cold atom sources