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High Quality Factor Dielectric Metasurfaces for Ultraviolet Circular Dichroism Spectroscopy
journal contribution
posted on 2019-11-13, 18:39 authored by Jack Hu, Mark Lawrence, Jennifer A. DionneChiral-optical spectroscopies, such as circular dichroism,
are
critical in the biomedical, pharmaceutical, and agrochemical industries
for revealing structural information about molecules and determining
the purity of chemical samples. Emerging nanophotonic platforms have
been shown to increase the intrinsically weak interaction between
circularly polarized light and chiral molecules through the concentration
of the local density of optical chirality, C. However,
enhancements in C have been limited to infrared and
visible frequencies, while the chiral absorption features of most
small molecules are in the ultraviolet. Furthermore, achievable C enhancements in nanophotonic systems remain relatively
low, especially when averaged across the sample volume. Here, we use
full-field simulations to design a high quality factor (high Q) diamond metasurface that enhances C by
over 3 orders of magnitude in the ultraviolet regime. The diamond
nanostructures enable ultraviolet Mie resonances while a biperiodic
disk lattice activates high Q resonances that significantly
increase the electromagnetic field intensities. When a high Q electric dipole and magnetic dipole mode are spatially
and spectrally overlapped, a Kerker-like condition emerges that enables
uniform sign C enhancements that are locally as high
as 1130-fold. Even when averaged across the unit cell and 40 nm away
from the surface, enhancements in C exceed 100-fold.
We show how the quality factor and C can be further
tuned by adjusting the structural asymmetry via the diameter offset
in the biperiodic lattice. Our results pave the way for ultrasensitive
chiral spectroscopy and efficient light-mediated enantiomer separation.
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Ultraviolet Circular Dichroism Spectroscopy Chiral-optical spectroscopiesuniform sign C enhancementsuse full-field simulationschiral absorption featuresquality factorultrasensitive chiral spectroscopynanophotonicresonancelight-mediated enantiomer separationHigh Quality Factor Dielectric Metasurfaceselectromagnetic field intensitiessamplemoleculebiperiodic disk lattice activates
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