Low-loss hybrid plasmonic modes guided by metal-coated dielectric wedges for subwavelength light confinement

TM01 mode in a cylindrical hybrid plasmonic waveguide with large propagation length

This study reports on a cylindrical hybrid plasmonic waveguide (CHPW) consisting of a high-index dielectric core, a sandwiched low-index dielectric layer, and a metal cladding. The CHPW supports the TM₀₁ mode with a radially polarized transverse component of the electric field. Optical fields can be significantly enhanced in the sandwiched low-index dielectric region with nanoscale thickness down to 5 nm, and tight mode confinement with the same order of the normalized mode area compared with that of the plasmonic waveguide is achieved. Moreover, the mode propagation loss is well compensated by adjusting dimensions of the waveguide to obtain a longer propagation distance. The calculated figure of merit reaches a value several times greater than that in the similarly reported structure. The results indicate that this novel type of hybrid structure can support the limited propagation of a radially polarized mode with good confinement and low loss, consummate the whole system of manipulating the cylindrical vector beams, and show great potential of applications for various integrated nano-photonic devices.

Sensitive method for measuring third order nonlinearities in compact dielectric and hybrid plasmonic waveguides

We demonstrate a sensitive method for the nonlinear optical characterization of micrometer long waveguides, and apply it to typical silicon-on-insulator nanowires and to hybrid plasmonic waveguides. We demonstrate that our method can detect extremely small nonlinear phase shifts, as low as 7.5·10<(-4) rad. The high sensitivity achieved imparts an advantage when investigating the nonlinear behavior of metallic structures as their short propagation distances complicates the task for conventional methods. Our results constitute the first experimental observation of χ((3)) nonlinearities in the hybrid plasmonic platform and is important to test claims of hybrid plasmonic structures as candidates for efficient nonlinear optical devices.

Utilization of Field Enhancement in Plasmonic Waveguides for Subwavelength Light-Guiding, Polarization Handling, Heating, and Optical Sensing

Plasmonic nanostructures have attracted intensive attention for many applications in recent years because of the field enhancement at the metal/dielectric interface. First, this strong field enhancement makes it possible to break the diffraction limit and enable subwavelength optical waveguiding, which is desired for nanophotonic integrated circuits with ultra-high integration density. Second, the field enhancement in plasmonic nanostructures occurs only for the polarization mode whose electric field is perpendicular to the metal/dielectric interface, and thus the strong birefringence is beneficial for realizing ultra-small polarization-sensitive/selective devices, including polarization beam splitters, and polarizers. Third, plasmonic nanostructures provide an excellent platform of merging electronics and photonics for some applications, e.g., thermal tuning, photo-thermal detection, etc. Finally, the field enhancement at the metal/dielectric interface helps a lot to realize optical sensors with high sensitivity when introducing plasmonic nanostrutures. In this paper, we give a review for recent progresses on the utilization of field enhancement in plasmonic nanostructures for these applications, e.g., waveguiding, polarization handling, heating, as well as optical sensing.

All-optical logic gates based on nonlinear plasmonic ring resonators

A nonlinear plasmonic T-shaped switch based on a square-shaped ring resonator is simulated by the finite-difference time-domain numerical method. Three optical logic gates-a NOT, with one T-shaped switch, and AND and NOR gates, each with two cascaded T-shaped switches-are proposed. The nonlinear Kerr effect is utilized to show the performance of our proposed logic gates. The values of transmission at the ON and OFF states of NOT and NOR gates are 70% and less than 0.6% of the input lightwave, respectively, while these values for the AND gate are 90% and less than 30%, respectively.

Elliptic cylindrical silicon nanowire hybrid surface plasmon polariton waveguide

We researched an elliptic cylindrical silicon nanowire hybrid surface plasmon polariton waveguide and evaluated its mode characteristics using the finite element method software COMSOL. The waveguide consists of three parts: an elliptic cylindrical silicon nanowire, a silver film layer, and a silica covering layer between them. All of the components are surrounded by air. After optimizing the geometrical parameters of the waveguide, we can achieve the waveguide's strong field confinement (ranging from λ²/270 to λ²/27) and long propagation distances (119-485 μm). In order to further understand the impact of the waveguide's architecture on its performance, we also studied the ridge hybrid waveguide. The results show that the ridge waveguide has moderate local field confinement ranging from λ²/190 to λ²/20 and its maximum propagation distance is about 340 μm. We compared the elliptic cylindrical and ridge nanowire hybrid waveguides with the cylindrical hybrid waveguide that we studied before. The elliptic cylindrical waveguide achieves a better trade-off between reasonable mode confinement and maximum propagation length in the three waveguides. The researched hybrid surface plasmon polaritons waveguides are useful to construct devices such as a directional coupler and may find potential applications in photonic integrated circuits or other novel SPP devices.

Tunable all-optical plasmonic rectifier in nanoscale metal-insulator-metal waveguides

We propose a tunable all-optical plasmonic rectifier based on the nonlinear Fano resonance in a metal-insulator-metal plasmonic waveguide and cavities coupling system. We develop a theoretical model based on the temporal coupled-mode theory to study the device physics of the nanoscale rectifier. We further demonstrate via the finite difference time domain numerical experiment that our idea can be realized in a plasmonic system with an ultracompact size of ~120×800  nm². The tunable plasmonic rectifier could facilitate the all-optical signal processing in nanoscale.

Investigation of 90° submicrometer radius bends of metal-insulator-silicon-insulator-metal waveguides

We theoretically and experimentally investigate 90° submicrometer radius bends (SRB) of metal-insulator-silicon-insulator-metal (MISIM) waveguides that are plasmonic waveguides fabricated with standard CMOS technology. We focus on the bends of MISIM waveguides with a wide (e.g., 160-220 nm) silicon line. This study shows that the bend efficiently turns the direction of the MISIM waveguide by 90° if its radius is about 0.7 μm. Moreover, we discuss the fact that the bend may be superior to a SRB of a silicon photonic waveguide when it is used to implement a ring resonator with a high quality factor and small volume.