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Chiral nanophotonic platforms provide a means of creating near fields with both enhanced asymmetric properties and intensities. They can be exploited for optical measurements that allow enantiomeric discrimination at detection levels > 6 orders of magnitude than is achieved with conventional chirally sensitive spectroscopic methods based on circularly polarized light. Here it is shown that surface enhanced Raman spectroscopy (SERS) is such a local probe of the near field environment. It is used to achieve enantiomeric discrimination of chiral helicoid nanoparticles deposited on left‐ and right‐handed enantiomorphs of a chiral metafilm using an achiral molecule as a probe. "Hotter" electromagnetic (EM) hotspots are created for matched combinations of helicoid and metafilms (left‐left and right‐right), while mismatched combinations leads to significantly "cooler" electromagnetic hotspots. This large enantiomeric dependency on hotspot intensity is readily detected using SERS with the aid of an achiral Raman reporter molecule. In effect SERS is used to distinguish between the different EM environments of the plasmonic diastereomers produced by mixing chiral nanoparticles and metafilms. The work demonstrates that by combining chiral nanophotonic platforms with established SERS strategies new avenues in ultrasensitive chiral detection can be opened. [ABSTRACT FROM AUTHOR]

Engineering optical emission from two-dimensional, transition metal dichalcogenides, such as tungsten disulfide (WS2), has implications in creating and understanding nanophotonic sources. One of the challenges in controlling the optical emission from two-dimensional materials is to achieve narrow angular spread using simple photonic geometry. In this article, we study how the photoluminescence of a monolayer WS2 can be controlled when coupled to a film coupled microsphere dielectric antenna. Specifically, by employing Fourier plane microscopy and spectroscopic techniques, we quantify the wavevector distribution in the momentum space. As a result, we show the beaming of the WS2 photoluminescence with angular divergence as low as θ 1 / 2 = 4.6°. Furthermore, the experimental measurements have been supported by three-dimensional numerical simulations. We envisage that the discussed results can be generalized to a variety of two-dimensional materials and can be harnessed for on-chip nonlinear and quantum technology. [ABSTRACT FROM AUTHOR]

Herein experimental evidence of directional surface enhanced Raman scattering from molecules situated inside a single nanowire–nanoparticle junction cavity is reported. The emission is confined to a narrow range of wavevectors perpendicular to the axis of the cavity. In addition to this, the molecules excite multiple guided modes of the nanowire which are imaged using leakage radiation Fourier microscopy. The emission wavevectors are further characterized as a function of output polarization. The excited guided modes of the wire show interesting polarization signatures. All the results are corroborated using finite element method based numerical simulations. Essentially, an important connection between gap‐cavity enhanced Raman scattering and its directionality of emission is provided. The results may be of relevance in understanding the cavity electrodynamics at the nanoscale and molecular coupling to extremely small gaps between a 1D and a 0D plasmonic nanostructure. [ABSTRACT FROM AUTHOR]

The generation and momentum space distribution of fluorescence emission from individual SiO2 microsphere on dye‐coated Au mirror are reported here. The molecular fluorescence emission mediated via whispering gallery modes of the sphere is studied using polarization‐resolved optical energy–momentum microspectroscopy. The experiments of this study reveal intensity dependence of split modes of the cavity as a function of in‐plane wavevector and emission polarization in the far field. The exotic far‐field distribution can be understood by sphere–image sphere model that further reveals the polarization dependence of the split modes. The presented results reveal the potential of metallo‐dielectric soft microcavities to engineer molecular emission that can encode spin and orbital angular momentum states and can be further extrapolated to realize dye‐loaded active meta‐atoms and meta‐surfaces. Vectorially polarized molecular fluorescence mediated through whispering gallery modes (WGMs) in microsphere coupled metallic film is demonstrated. The coupling between microsphere and its image results in splitting of WGMs, which induces vectorial polarization structure to the molecular fluorescence. This work can be extrapolated to understand the effect of complex polarization structure in strong coupling physics. [ABSTRACT FROM AUTHOR]