Conditions for Enhancing Chiral Nanophotonics near Achiral Nanoparticles

Raziman, T. V.; Godiksen, Rasmus H.; Müller, Moos A.; Curto, Alberto G.

doi:10.1021/acsphotonics.9b01200

Cited by 43 publications

(45 citation statements)

References 47 publications

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“…[ 35–38 ] Specifically, helicity‐preserving metasurfaces composed of sub‐wavelength, 2D dielectric disk arrays have received significant attention for supporting highly twisted electromagnetic near‐fields. [ 39–45 ] While similarly structured Si arrays coated with Ni have been shown to strengthen MO effects with linear excitation, [ 46–48 ] the capability of these metasurfaces to shape CPL by concentrating absolute electric field rotation near and within magnetic thin films has not yet been explored.…”

Section: Figurementioning

confidence: 99%

Helicity‐Preserving Metasurfaces for Magneto‐Optical Enhancement in Ferromagnetic [Pt/Co]_N Films

Abendroth

Solomon

Barton

et al. 2020

Advanced Optical Materials

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materials, i.e., Faraday and Kerr effects, and magnetic circular dichroism (MCD). Circularly polarized light (CPL) pulses may also induce transient effective magnetic fields via the inverse Faraday effect (IFE), used to excite coherent spin precession at GHz and THz frequencies. [7,8] Of particular interest for manipulating magnetic order at ultrafast timescales with CPL is all-optical helicity-dependent switching (AO-HDS), which has been observed in ferromagnetic, ferrimagnetic, and granular thin films that exhibit perpendicular magnetic anisotropy. [9-12] However, contributions from MCD and the IFE to AO-HDS are difficult to deconvolve, [13-17] and understanding all-optical switching remains a challenging and widely debated topic in photonics and magnetism. [13,18-20] Enhancing local electric field rotation with CPL excitation could provide mechanistic insight, elucidate strategies toward faster and more efficient helicity-mediated switching with high spatial resolution, [21,22] and increase overall MO response for light-assisted reading and writing, essential for high-density on-chip integration. [23] Efforts to enhance MO effects below the diffraction limit and to advance the tunability of photon-electron spin interactions have been dominated by magnetoplasmonic approaches, which use localized surface plasmon resonances in metallic nanostructures or propagating surface plasmon polaritons at metal-dielectric interfaces. [24-32] For example, gold nanoparticle antennas have been used to achieve nanoconfined all-optical switching in TbFeCo films. [33] More recently, plasmon-mediated enhancement of the IFE by two orders of magnitude was shown to realize sub-THz spin precession confined within 100 nm thick regions of GdYbBIG. [34] However, plasmonic metals suffer from high intrinsic losses, and excessive heating could limit their performance near optical frequencies. Alternatively, greater efficiency could be realized with low-loss dielectric nanostructures fabricated from high-index materials that offer additional control over phase and polarization of light by virtue of their electric and magnetic Mie modes. [35-38] Specifically, helicity-preserving metasurfaces composed of sub-wavelength, 2D dielectric disk arrays have received significant attention for supporting highly twisted electromagnetic near-fields. [39-45] All-optical control and detection of magnetic states for high-density recording necessitate nanophotonic approaches to amplify local light intensity below the diffraction limit. Sculpting the near-field phase and polarization can additionally strengthen magneto-optical effects that rely on circularly polarized pulses, such as all-optical helicity-dependent switching, imaging, and spin-wave excitation. Here, high-refractive-index dielectric nanoantennas illuminated with circularly polarized light resonantly enhance local electric field rotation by more than sixfold within [Pt/Co] N thin films. Sub-wavelength arrays of amorphous Si nanodisks, or metasurfaces, patterned on perpendicularly magnetized film...

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Section: Figurementioning

confidence: 99%

Helicity‐Preserving Metasurfaces for Magneto‐Optical Enhancement in Ferromagnetic [Pt/Co]_N Films

Abendroth

Solomon

Barton

et al. 2020

Advanced Optical Materials

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“…[ 25–30 ] Dielectric nanoparticles have also enabled nonradiating anapole modes, [ 31,32 ] and very high‐ Q modes related to Fano resonances and bound states in the continuum. [ 33 ] Dielectric metasurfaces could find applications in color displays, [ 34–36 ] photoluminescence control, [ 37–39 ] magneto‐optical effect modulation, [ 40,41 ] sensing, [ 42 ] holography, [ 43 ] and light harvesting for detectors and solar cells. [ 44 ]…”

Section: Introductionmentioning

confidence: 99%

Enhanced Light Emission by Magnetic and Electric Resonances in Dielectric Metasurfaces

Murai

Castellanos

Raziman

et al. 2020

Advanced Optical Materials

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An enhanced emission of high quantum yield molecules coupled to dielectric metasurfaces formed by periodic arrays of polycrystalline silicon nanoparticles is demonstrated. Radiative coupling of the nanoparticles, mediated by in‐plane diffraction, leads to the formation of collective Mie scattering resonances or Mie surface lattice resonances (M‐SLRs), with remarkable narrow line widths. These narrow line widths and the intrinsic electric and magnetic dipole moments of the individual Si nanoparticles allow resolving electric and magnetic M‐SLRs. Incidence angle‐ and polarization‐dependent extinction measurements and high‐accuracy surface integral simulations show unambiguously that magnetic M‐SLRs arise from in‐ and out‐of‐plane magnetic dipoles, while electric M‐SLRs are due to in‐plane electric dipoles. Pronounced changes in the emission spectrum of the molecules are observed, with almost a 20‐fold enhancement of the emission in defined directions of molecules coupled to electric M‐SLRs, and a fivefold enhancement of the emission of molecules coupled to magnetic M‐SLRs. These measurements demonstrate the potential of dielectric metasurfaces for emission control and enhancement, and open new opportunities to induce asymmetric scattering and emission using collective electric and magnetic resonances.

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“…On the other hand, tuned resonant peaks destroy the phase condition, resulting again in suboptimal optical chirality. 9 , 34 …”

Section: Introductionmentioning

confidence: 99%

Dual Nanoresonators for Ultrasensitive Chiral Detection

et al. 2021

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The discrimination of enantiomers is crucial in biochemistry. However, chiral sensing faces significant limitations due to inherently weak chiroptical signals. Nanophotonics is a promising solution to enhance sensitivity thanks to increased optical chirality maximized by strong electric and magnetic fields. Metallic and dielectric nanoparticles can separately provide electric and magnetic resonances. Here we propose their synergistic combination in hybrid metal–dielectric nanostructures to exploit their dual character for superchiral fields beyond the limits of single particles. For optimal optical chirality, in addition to maximization of the resonance strength, the resonances must spectrally coincide. Simultaneously, their electric and magnetic fields must be parallel and π/2 out of phase and spatially overlap. We demonstrate that the interplay between the strength of the resonances and these optimal conditions constrains the attainable optical chirality in resonant systems. Starting from a simple symmetric nanodimer, we derive closed-form expressions elucidating its fundamental limits of optical chirality. Building on the trade-offs of different classes of dimers, we then suggest an asymmetric dual dimer based on realistic materials. These dual nanoresonators provide strong and decoupled electric and magnetic resonances together with optimal conditions for chiral fields. Finally, we introduce more complex dual building blocks for a metasurface with a record 300-fold enhancement of local optical chirality in nanoscale gaps, enabling circular dichroism enhancement by a factor of 20. By combining analytical insight and practical designs, our results put forward hybrid resonators to increase chiral sensitivity, particularly for small molecular quantities.

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Conditions for Enhancing Chiral Nanophotonics near Achiral Nanoparticles

Cited by 43 publications

References 47 publications

Helicity‐Preserving Metasurfaces for Magneto‐Optical Enhancement in Ferromagnetic [Pt/Co]_N Films

Helicity‐Preserving Metasurfaces for Magneto‐Optical Enhancement in Ferromagnetic [Pt/Co]_N Films

Enhanced Light Emission by Magnetic and Electric Resonances in Dielectric Metasurfaces

Dual Nanoresonators for Ultrasensitive Chiral Detection

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Conditions for Enhancing Chiral Nanophotonics near Achiral Nanoparticles

Cited by 43 publications

References 47 publications

Helicity‐Preserving Metasurfaces for Magneto‐Optical Enhancement in Ferromagnetic [Pt/Co]N Films

Helicity‐Preserving Metasurfaces for Magneto‐Optical Enhancement in Ferromagnetic [Pt/Co]N Films

Enhanced Light Emission by Magnetic and Electric Resonances in Dielectric Metasurfaces

Dual Nanoresonators for Ultrasensitive Chiral Detection

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Product

Resources

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Helicity‐Preserving Metasurfaces for Magneto‐Optical Enhancement in Ferromagnetic [Pt/Co]_N Films

Helicity‐Preserving Metasurfaces for Magneto‐Optical Enhancement in Ferromagnetic [Pt/Co]_N Films