Metal Nanoridges in Hollow Si-Loaded Plasmonic Waveguides for Optimal Mode Properties and Ultra-Compact Photonic Devices

Abstract

To achieve subwavelength mode confinement, we propose a hybrid plasmonic waveguide consisting of a metal nanoridge embedded in a silica-covered hollow silicon ridge waveguide on a metal substrate. The mode confinement, propagation length, and figure of merit are optimized by controlling the geometry of the waveguide. At the optimal figure of merit, the normalized mode area of 3.0 × 10 −3 (λ 2 /4) is achieved while retaining a propagation length of 163.0 μm at the telecom wavelength of 1550 nm. The coupling strength of a directional coupler composed of two such waveguides is analyzed to examine the degree of integration of photonic integrated circuits. A strong dependence on the coupling length makes the proposed structure very favorable for use in various plasmonic devices. Furthermore, transmission through a 90 • bend (studied to examine the compactness of the proposed waveguide), is observed to be 80% at the small radius of curvature of 0.7 μm.

Mode confinement enhanced in hybrid Bloch surface wave long-range waveguide

“…By combining high-index dielectric nanowires with the metallic structures to couple with the plasmonic mode, the high-refractive index contrast could facilitate strong hybridization between dielectric modes and SPP modes, leading to nanoscale mode area with reasonable propagation length 19 – 21 Based on this metal/dielectric hybridized structure, tremendous work has been placed on exploring high-quality HPW waveguiding schemes, including low-loss long-range SPP, 22 subwavelength localized SPP in metal wedges, 23 and ridges, 24 , 25 as well as hybrid metal-dielectric slot waveguides 26 , 27 . Their unique capability could provide improved optical performance in achieving reasonable propagation length of tens of microns while maintaining subwavelength mode confinement ability, thus, enabling a number of high-performance and fascinating optical applications.…”

Analysis of convex rib hybrid surface plasmon waveguide with ultralong propagation distance and tight mode confinement

“…Owing to these excellent characteristics, a variety of modified HSPWG structures such as long-range HSPWG, 5 ridge HSPWG, 6 V-groove HSPWG, 7 and graphene HSPWG 8 is further investigated by many research groups. These modified HSPWG structures are potentially excellent candidates exploited as directional couplers 9 and polarization rotators.…”

Highly confined guiding of low-loss plasmon waves in hybrid metal-dielectric slot waveguides

“…In addition to the conventional HPWs being studied, including standard configurations that consist of high-index dielectric nanostructures placed in close vicinity to metallic surfaces [24,26,29] and silicon-based waveguides composed of truncated metallic films in proximity to silicon-on-insulator (SOI) substrates [30,35,78], recent years have also witnessed an emerging class of modified hybridized waveguiding configurations with unique optical features [79]. Based on the hybridization between dielectric and various plasmon modes such as long-range surface plasmon polaritons [32,48,53,80] and highly confined plasmonic modes in metal wedge [43,51,81]/ridge [49,82]/slot [34,[44][45][46]/nanowire [33,36,50,54] waveguides, these modified HPWs hold the promise of enhancing the guiding performance of their traditional hybrid counterparts. However, for these modified structures, it is still challenging to simultaneously realize reduced propagation loss and enhanced field confinement as compared to the traditional HPWs.…”