Narrow Results

The near-field distribution of surface plasmon polariton (SPP) on metallic photonic crystal slabs has been studied. Preliminary numerical simulations indicate that the interference of SPP on the exit side of metallic photonic crystal slabs can redistribute the illumination light into nano-scale spatial distribution, which beats the Rayleigh diffraction limit. The electric field distribution of SPP with a resolution of 50 nm was measured by recording the high intensity range into photoresist with a wavelength of 436 nm. Because of the small wavelength of the plasmon wave, a much higher spatial resolution can be obtained, which can provide a new nano-fabrication or nano-storage method by using optical light with a long wavelength.

The transmission properties of rectangular one-dimensional unperforated metallic periodic structures for frequencies close to the surface plasmon band are investigated experimentally and theoretically. The results reveal that it is possible to obtain unexpectedly large transmissions through thick unperforated metallic structures. The mechanisms of enhanced transmissions are attributed to resonant excitations of three kinds of plasmon radiations: coupled surface plasmon polaritons, horizontal localized groove plasmon mode, and vertical localized groove plasmons mode. Once the surface plasmon polaritons and the vertical groove plasmon modes are excited simultaneously, the transmission approaches to maximum at the coincident condition.

The spatial distribution of the interference of surface plasmon polariton (SPP) on metallic nanostructures has been studied. The results show that the transmission of electromagnetic radiation is remarkably enhanced for frequencies close to the surface plasmon band and the interference of SPP can redistribute the illumination light into subwavelength-scale spatial distribution with high intensity, which beats the Rayleigh diffraction limit. For an appropriate thickness, the transmission of an unperforated structure can be larger than that of holes or slits systems with the same periodicity and thickness when the coupled surface plasmon wave mode is excited. With the help of the interference of the horizontal plasmon excited by Bragg resonance due to the periodicity in the horizontal direction, the vertical plasmons, excited in z direction via Fabry–Perot cavity resonance in different grooves, are correlated, so the transmission is increased via the tunneling process. The properties of transparency for light but impenetrability for gas and liquid will be of importance for device applications. The information on near-field distribution from perforated metallic structures is important for understanding the underlying physics, as well as for optimizing photonic crystals for possible applications.

A mode separation approach in the nanoring resonator by a cascaded slot cavity is proposed and numerically investigated using the finite-difference time-domain (FDTD) method. With the cascaded slot cavity, the specified modes in the nanoring can be separated to realize a wide free spectral range (FSR) or single channel filtering, which provides a free degree to the plasmonic filters design. Simulation results also demonstrate that the full-width at half-maximum (FWHM) of the single channel filter obtained from the cascaded slot cavity can be effectively reduced to meet various requirements.

In this paper, a wide-angle polarization-sensitive dual-band absorber at infrared wavelengths with a multilayer grating is reported. The simulation results show that the absorber has two absorption peaks at wavelengths λ = 1.365 μm and λ = 3.035 μm with the absorption magnitudes more than 0.97 and 0.99 for TM polarization (electric field perpendicular to the strips), respectively. And this absorber reflects almost all TE polarization (electric field parallel to the strips) light. The dual-band absorption peaks can be tuned by varying the width of the strips, and the absorption magnitudes are more than 0.9 for the dual-band absorption peaks for angles up to 70°.

We report a multiband absorber with dielectric–dielectric–metal structure in the infrared regime. The simulation results show that that near-perfect absorption is originated from the guide mode resonance and surface plasmonic polaritons (SPPs) excitation. Furthermore, the absorption peaks of this multiband absorber can be tuned by changing the incidence angle or scaling the microstructure dimensions. The results of this study have possible future potential applications in thermal emitter and sensor.

In this paper we review a new electro-optic devices design strategy using long range surface plasmon (LRSP) excitation along subwavelength metal grating. It is shown that LRSP can be excited on extremely thin subwavelength metal grating embedded in symmetric dielectric ambient. Due to coupling and propagation of LRSP between the metal grating nanowires, a super-narrow reflection dip can be obtained. Compared with conventional LRSP along metal thin film, much narrower resonance is achieved through decreased damping from the existence of large dielectric gaps between the grating nanowires. This interesting phenomenon can be used to design electro-optics devices with improved performance. Examples of electro-optic modulator design with lower insertion loss and low operating voltage and spectral notch filter design with very narrow spectral width will be shown. Its application in refractive index sensing is also discussed.

Modal characteristics of plasmonic nanostrip waveguides (PNWGs) have been analyzed for their use in the design of functional plasmonic devices. Also, the beat lengths of the plasmonic nanostrip directional coupler and the multimode interference (MMI) coupler, have been analyzed. We found a peculiar phenomenon in the direction coupler, which makes the coupling length zero and does not allow the optical coupling between two parallel PNWGs. We also found that there exists a minimal beat length in the gap between the two metal films in the MMI coupler. From these results a nano-ring resonator switch and a MMI wavelength splitter were designed.

Using hydrodynamic theory of electron gas motion in metals, we obtain hyperpolarizability of the metal hemisphere in the framework of the quasistatic approach. For a silver hemisphere placed on a glass substrate and covered with TiO₂ shell, we demonstrate analytically that conduction electrons in the vicinity of the hemisphere sharp edge dominate the nonlinear optical response of the nanoparticle. The developed theory is verified by numerical simulation in COMSOL. Numerical analysis reveals that rounding of the sharp edge affects the linear polarizability and first hyperpolarizability of the hemisphere differently. We also discuss dependence of the hyperpolarizability on the dielectric shell thickness and show that both lacking of the inversion symmetry and presence of the glass–air-TiO₂ interface essentially contribute to the polarizability of the hemisphere at the frequency of the second harmonic.

Here, we propose a novel plasmonic structure, called asymmetric plasmonic nanocavity grating (APNCG), which is shown to dramatically enhance nonlinear optical process of second harmonic generation (SHG). The proposed structure consists of two different metals on both sides of lithium niobate and a thin layer of graphene. By using two different metals the nonlinear susceptibility of the waveguide would be increased noticeably causing to increase SHG. On the other hand, it consists of two identical gratings on one side. By two identical gratings, the pump beam is coupled to two opposing SPP waves, which interfere with each other and result in SPP standing wave in the region between the two gratings. The distance between two gratings will be optimized to reach the highest SHG. It will be shown that by optimizing the geometry of proposed structure and using different metals, field enhancement in APNCG waveguides can result in large enhancement of SHG.

Nonlinear plasmonic metasurfaces have recently attracted considerable interest, due to their potential for enabling nanoscale nonlinear optics. Here, we review the current progress in this topic while paying special attention to existing challenges. In order to limit our scope, we concentrate on nonlinear metasurfaces utilizing inter-particle and lattice effects and focus on metasurfaces operating close to visible and near-infrared frequencies. We will also critically discuss the short and longer term prospects of nonlinear metasurfaces to start rivaling traditional nonlinear materials in applications.

We propose a scheme of terahertz (THz) indirect detection via plasmonic-antenna enhanced sum frequency generation process, where the THz wave is converted to optical wave that is detected by photodetector. The gold antenna built in the structure can improve the conversion efficiency by enhancing both the optical wave and THz wave. The numerical simulations show that the field enhancement is influenced by the geometry of the antenna, so the conversion efficiency can be improved highly by optimizing the antenna. Compared with commercial detectors, our detection system has a much lower noise equivalent power (NEP) of 15.4pW/$\sqrt{\mathrm{\text{Hz}}}$ at 5THz.

In this paper, surface plasmons polariton propagation and manipulation is reviewed in the context of experiments and modeling of optical images. We focus our attention in the interaction of surface plasmon polaritons with arrays of micro-scatereres and nanofabricated structures. Numerical simulations and experimental results of different plasmonic devices are presented. Plasmonic beam manipulation opens up numerous possibilities for application in biosensing, nanophotonics, and in general in the area of surface optics properties.