Surface plasmon polariton (SPP) coupling is a basic subject for plasmonic study and applications. Optical nanoantennas enable downscaling of the SPP coupling to subwavelength scales. In this study, asymmetric optical slot nanoantenna pairs composed of two optical slot nanoantennas with different lengths are proposed for SPP directional coupling. Broadband unidirectional launching of SPPs is achieved, and the extinction ratio obtained experimentally reaches up to 44. The bandwidth is larger than 157 nm. Furthermore, SPP direction-selective radiation is demonstrated using the asymmetric optical slot nanoantenna pairs. A novel plasmonic display device showing the propagation direction of SPPs is achieved by employing asymmetric optical slot nanoantenna pairs without any electric device. Asymmetric optical slot nanoantenna pairs have large potential in the directional control of SPP launching and radiation and can be very useful in compact optical circuits and other photonic integrations.

Understanding the unique characteristics of plexcitons, hybridized states resulting from the strong coupling between plasmons and excitons, is vital for both fundamental studies and practical applications in nano-optics. However, the research of plexcitons from the perspective of chiral optics has been rarely reported. Here, we experimentally investigate the optical chirality of plexcitonic systems consisting of composite metal nanoparticles and chiral J-aggregates in the strong coupling regime. Mode splitting and anticrossing behavior are observed in both the circular dichroism (CD) and extinction spectra of the hybrid nanosystems. A large mode splitting (at zero detuning) of up to 136 meV/214 meV in CD/extinction measurements confirms that the systems attain the strong coupling regime. This phenomenon indicates that the formation of plexcitons modifies not only the extinction but also the optical chirality of the hybrid systems. We develop a quasistatic theory to elucidate the chiral optical responses of hybrid systems. Furthermore, we propose and justify a criterion of strong plasmon–exciton interaction: the mode splitting in the CD spectra (at zero detuning) is larger than half of that in the extinction spectra. Our findings give a chiral perspective on the study of strong plasmon–exciton coupling and have potential applications in the chiral optical field.

We propose a refractive index sensor based on the interference of two surface-plasmon waves on both surfaces of a gold film with a two-slit structure. The phase of the interference was solved, and the dispersion relation of the real part of Au dielectric function was considered. The sensor was performed with NaCl-H2O solutions of different concentrations and exhibited a linear response and a high sensitivity of 4547 nm/RIU (refractive index unit) to the refractive index change.

Full metal various nanostructures with extremely smooth surface, small feature size and high aspect ratio can be fabricated by a template stripping method with EBL-patterned PMMA layer as a template. It is further demonstrated that our method is crucial to obtain clear and abundant plasmonic modes in nanocavities with metal reflectors.

The Talbot effect of the surface plasmon polaritons (SPPs) using SPP launching gratings is studied experimentally. Talbot carpets are obtained and the Talbot distance is given when the paraxial approximation is not satisfied. Multi-layer and multi-level-phase launching gratings are designed to enhance the intensities of the amplitude-modulated revivals. Effective focusing of SPPs with multiple focal spots and a subwavelength full width at half maximum is obtained by using a three-layer four-level-phase launching grating.

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Broadband spin‐controlled surface plasmon polariton (SPP) launching and radiation via L‐shaped optical slot nanoantennas are proposed and demonstrated experimentally. The phase retardation and spectra overlapping between two resonant plasmon modes in the L‐shaped optical slot nanoantenna lie at the origin of this effect. SPP launching in two perpendicular directions are controlled by the spin of the incident light. Broadband directional launching of SPPs is achieved and the extinction ratio keeps larger than 7 dB within a wavelength range of 150 nm. Furthermore, the photon spin of SPP radiation via the L‐shaped optical slot nanoantennas is controlled by SPP propagation directions. These investigations provide a route for spin‐controlled nanophotonic applications.

We designed a heterogeneous optical slot antenna (OSA) that is capable of detecting single molecules in solutions at high concentrations, where most biological processes occur. A heterogeneous OSA consists of a rectangular nanoslot fabricated on heterogeneous metallic films formed by sequential deposition of gold and aluminum on a glass substrate. The rectangular nanoslot gives rise to large field and fluorescence enhancement for single molecules. The near-field intensity inside a heterogeneous OSA is 170 times larger than that inside an aluminum zero-mode waveguide (ZMW), and the fluorescence emission rate of a molecule inside the heterogeneous OSA is about 70 times higher than that of the molecule in free space. Our proposed heterogeneous optical antenna enables excellent balance between performance and cost. The design takes into account the practical experimental conditions so that the parameters chosen in the simulation are well within the reach of current nano-fabrication technologies. Our results can be used as a direct guidance for designing high-performance, low-cost plasmonic nanodevices for the study of bio-molecule and enzyme dynamics at the single-molecule level.