Towards rational design and optimization of near-field enhancement and spectral tunability of hybrid core-shell plasmonic nanoprobes

Gap-enhanced optical bistability in plasmonic core-nonlinear shell dimers

Localized surface plasmon resonance in capacitively-coupled metallic nanoparticle dimers accompanied by a substantial local field enhancement in the interparticle gap area can enable boosting of nonlinear optical effects. In this paper, we analyze optical bistability in a plasmonic spherical dimer wrapped by a mutual nonlinear shell. In the common graphical post-processing technique of optical bistability, it is assumed that the refractive index change is homogeneous throughout the whole shell. However, we resolve this issue by taking into account the inhomogeneous nature of the power density in the dimer and linking the refractive index change to the local intensity inside the shell. The hysteresis branches of the normalized scattering and extinction cross-sections, as well as electric near-field strength, were derived by increasing and decreasing the driving field intensity. The analysis shows that optical bistability in the dimer with a 3 nm gap can be achieved at switching intensities of about 375 kW cm-2 and 225 kW cm-2, where each stable state of the C-Sh dimer corresponds to a certain plasmonic mode. The range of driving field intensities can be further decreased by considering smaller interparticle distances. The influence of the nonlinear shell on the spectral response is also examined. Suggested configurations distributed on a planar dielectric substrate have potential applications as all-optical switches and memory elements.

Sensors for Detection of the Synthetic Dye Rhodamine in Environmental Monitoring Based on SERS

This article presents a review of many types of SERS sensors for food safety and environmental pollution monitoring based on detecting rhodamine. It introduces the basic concepts of substrates, enhancement factors, and mechanisms, devices' sensors integrated with the microstructure. Here, we review the state-of-the-art research in the field of rhodamine monitoring and highlight the applications of SERS sensors. The trends in the development of substrates for different applications have been mentioned with the aim of providing an overview of the development of different SERS substrates. Thus, an efficient approach for rhodamine detection has a good perspective for application in environmental monitoring.

Enhanced Absorption with Graphene-Coated Silicon Carbide Nanowires for Mid-Infrared Nanophotonics

The mid-infrared (MIR) is an exciting spectral range that also hosts useful molecular vibrational fingerprints. There is a growing interest in nanophotonics operating in this spectral range, and recent advances in plasmonic research are aimed at enhancing MIR infrared nanophotonics. In particular, the design of hybrid plasmonic metasurfaces has emerged as a promising route to realize novel MIR applications. Here we demonstrate a hybrid nanostructure combining graphene and silicon carbide to extend the spectral phonon response of silicon carbide and enable absorption and field enhancement of the MIR photon via the excitation and hybridization of surface plasmon polaritons and surface phonon polaritons. We combine experimental methods and finite element simulations to demonstrate enhanced absorption of MIR photons and the broadening of the spectral resonance of graphene-coated silicon carbide nanowires. We also indicate subwavelength confinement of the MIR photons within a thin oxide layer a few nanometers thick, sandwiched between the graphene and silicon carbide. This intermediate shell layer is characteristically obtained using our graphitization approach and acts as a coupling medium between the core and outer shell of the nanowires.