Luna Cui

Spectral Splitting Based on Electromagnetically Induced Transparency in Plasmonic Waveguide Resonator System

Spectral splitting is numerically investigated based on the electromagnetically induced transparency (EIT) in a nanoscale plasmonic waveguide resonator system, which consists of a square ring resonator coupled with a stub-shaped metal-insulator-metal (MIM) waveguide. Simulation results show that the transparency window can be easily tuned by changing the geometrical parameters of the structure and the material filled in the resonators. By adding another stub or (and) square ring resonator, multi-EIT-like peaks appear in the broadband transmission spectrum, and the physical mechanism is presented. Our compact plasmonic structure may have potential applications for nanoscale optical switching, nanosensor, nanolaser, and slow-light devices in highly integrated optical circuits.

TUNABLE BAND-STOP PLASMONIC FILTER BASED ON SYMMETRICAL TOOTH-SHAPED WAVEGUIDE COUPLES

A simple plasmonic filter with symmetrical tooth-shaped waveguides is proposed and investigated by using finite element method. It is found that the structure with a single symmetrical tooth-shaped waveguide couple can realize a tunable band-stop filter. Attributed to cascaded symmetrical tooth-shaped waveguide couples, the structure can achieve a flat band-stop response with no intensity variation over the transmission spectrum. And the central wavelength of the stopband linearly increases with the simultaneous increasing of depths of waveguides. Moreover, reduced structure size can be achieved by controlling the dielectric constant of the medium.

Optical bistability of surface plasmon polaritons in nonlinear Kretschmann configuration

Optical bistability based on surface plasmon polaritons in the Kretschmann configuration involving a Kerr nonlinear medium is described by analytical solutions. The conditions of forming the optical bistability with different parameters are explored. The resonant angle of surface plasmon polaritons varying with the incident light intensity also generates the phenomenon of bistability. The system could form optical bistability with the special thickness of the metal film and incident angle. This kind of system has potential application in all-optical networks.

Refractive Plasmonic Sensor Based on Fano Resonances in an Optical System

A symmetric plasmonic structure consisting of metal–insulator–metal waveguide, groove and slot cavities is studied, which supports double Fano resonances deriving from two different mechanisms. One of the Fano resonances originates from the interference between the resonances of groove and slot cavities, and the other comes from the interference between slot cavities. The spectral line shapes and the peaks of the double Fano resonances can be modulated by changing the length of the slot cavities and the height of the groove. Furthermore, the wavelength of the resonance peak has a linear relationship with the length of the slot cavities. The proposed plasmonic nanosensor possesses a sensitivity of 800 nm/RIU and a figure of merit of 3150, which may have important applications in switches, sensors, and nonlinear devices.

Effect of ridge morphologies on surface plasmon scattering by subwavelength surface ridges

Surface plasmon scattering by two-dimensional ridges has been studied, mainly in the optical regime. Both the overall width and height of the ridges are fixed. The scattering properties are numerically investigated by the three-dimensional full-vector finite-difference time-domain method, with morphologies regularly changed by subdividing the width and the height of the ridges simultaneously. The results show that the transmission can be improved and the reflection reduced by increasing the degree of subdivision, which makes the surfaces of ridges much smoother. Meanwhile, morphology has little influence on the radiation, which may be attributed to the unchanged total surface area of the ridges. Moreover, we analyze the scattering of SPPs by arrays of ridges.

Polarization-dependent plasmon mode mapping of Ag nanowires based on two-photon excitation fluorescence of quantum dots

We show that the plasmon modes of Ag nanowires can be imaged by coating them with a layer of quantum dots (QDs), held off the nanowire surface by a nanoscale dielectric spacer layer. Parallel or perpendicular excitation polarization modulates the intensity maps of two-photon excitation fluorescence (TPEF), which exhibit Fabry–Perot cavity modes at the excitation or fluorescence wavelength. We attribute this phenomenon to the QDs excited by propagating surface plasmon polaritons or localized surface plasmon modes. The results of the TPEF intensity maps are well explained by theoretical simulations, and the energy transfer process is also discussed.