A Triangle Hybrid Plasmonic Waveguide with Long Propagation Length for Ultradeep Subwavelength Confinement

Facing the problems of ohmic loss and short propagation length, the application of plasmonic waveguides is limited. Here, a triangle hybrid plasmonic waveguide is introduced, where a cylinder silicon waveguide is separated from the triangle prism silver waveguide by a nanoscale silica gap. The process of constant optimization of waveguide structure is completed and simulation results indicate that the propagation length could reach a length of 510 μm, and the normalized mode area could reach 0.03 along with a high figure of merit 3150. This implies that longer propagation length could be simultaneously achieved along with relatively ultra-deep subwavelength mode confinement due to the hybridization between metallic plasmon polarization mode and silicon waveguide mode, compared with previous study. By an analysis of fabrication errors, it is confirmed that this waveguide is fairly stable over a wide error range. Additionally, the excellent performance of this is further proved by the comparison with other hybrid plasmonic waveguides. Our work is significant to manipulate light waves at sub-wavelength dimensions and enlarge the application fields, such as light detection and photoelectric sensors, which also benefit the improvement of the integration of optical devices.

Half-mode substrate integrated plasmonic waveguide for filter and diplexer designs

A half-mode substrate integrated waveguide (HMSIW) combined with spoof surface plasmon polariton (SSPP) structure is proposed to realize bandpass filter (BPF) characteristic and miniaturization, which is termed as the half-mode substrate integrated plasmonic waveguide (HMSIPW). Compared with the conventional HMSIW structure having identical cutoff frequency, this new design of HMSIPW not only supports SSPP modes, but also realizes a transversal size reduction of 19.4% and longitudinal reduction of more than 60%. Then, a diplexer based on two back-to-back placed HMSIPW BPFs is designed, and it has only one row of metallized via holes to further reduce the transversal size. The experimental prototypes of the filters and diplexer have been manufactured, and the measurement results agree well with simulation ones. Due to the size miniaturization and simple structure, the proposed designs will have many potentials in the integrated devices and circuits for wireless communication systems.

Theoretical Investigation of an Air-Slot Mode-Size Matcher between Dielectric and MDM Plasmonic Waveguides

Hybrid integration of dielectric and plasmonic waveguides is necessary to reduce the propagation losses due to the metallic interactions and support of nanofabrication of plasmonic devices that deal with large data transfer. In this paper, we propose a direct yet efficient, very short air-slot coupler (ASC) of a length of 36 nm to increase the coupling efficiency between a silicon waveguide and a silver-air-silver plasmonic waveguide. Our numerical simulation results show that having the ASC at the interface makes the fabrication process much easier and ensures that light couples from a dielectric waveguide into and out of a plasmonic waveguide. The proposed coupler works over a broad frequency range achieving a coupling efficiency of 86% from a dielectric waveguide into a metal-dielectric-metal (MDM) plasmonic waveguide and 68% from a dielectric waveguide to an MDM plasmonic waveguide and back into another dielectric waveguide. In addition, we show that even if there are no high-precision fabrication techniques, light couples from a conventional dielectric waveguide (CDW) into an MDM plasmonic waveguide as long as there is an overlap between the CDW and ASC, which reduces the fabrication process tremendously. Our proposed coupler has an impact on the miniaturization of ultracompact nanoplasmonic devices.