Ultrashort broadband polarization beam splitter based on a combined hybrid plasmonic waveguide

Abstract

We propose an ultracompact broadband polarization beam splitter (PBS) based on a combined hybrid plasmonic waveguide (HPW). The proposed PBS separates transverse-electric (TE) and transverse-magnetic (TM) modes using a bent lower HPW with vertical nanoscale gaps and a straight upper HPW with a horizontal nanoscale gap, respectively, without relying on an additional coupling region. This design considerably reduces the length of the PBS to the submicron scale (920 nm, the shortest PBS reported to date) while offering polarization extinction ratios (PERs) of ~19 dB (~18 dB) and insertion losses (ILs) of ~0.6 dB (~0.3 dB) for the TE (TM) mode over an extremely broad band of 400 nm (from λ = 1300 nm to 1700 nm, covering entirely second and third telecom windows). The length of the designed PBS can be reduced further to 620 nm while still offering PERs of 15 dB, realizing a densely photonic integrated circuit. Considering the fabrication tolerance, the designed PBS allows for large geometrical deviations of ±20 nm while restricting PER variations to within 1 dB, except for those in the nanoscale gaps smaller than 10nm. Additionally, we also address the input and ouput coupling efficiencies of the proposed PBS.

Compact and fabrication-tolerant polarization splitter based on horizontal triple-slot waveguide

“…Many approaches, including various design approaches and materials, have been reported to build a PBS [7][8][9][10][11]. One approach could be the use of a hybrid plasmonic waveguide (HPW), which has been extensively studied and can yield an ultra-compact broadband PBS [12]. Nevertheless, a HPW suffers from the inherent metallic absorption and complicated fabrication process.…”

On-chip polarization splitter based on a multimode plasmonic waveguide

“…Surface plasmon polaritons (SPPs), which can significantly shrink the device dimensions because of the subwavelength field confinements [15], show great potential in improving the integration density of the PICs [16,17]. Because of the polarization dependence of the SPPs, a variety of hybrid plasmonic waveguide structures, which supported both the transverse magnetic (TM) and transverse electric (TE) waveguide modes, were designed to downscale the footprints of the PBSs [18][19][20][21][22][23][24]. For example, by introducing silver cylinders in the two-silicon-waveguide structure to construct a hybrid waveguide, the PBS with a footprint of only about 3.5 μm × 1.9 μm was numerically predicted based on directional coupling [19].…”

“…By covering a metal strip on the silicon waveguide to form the hybrid waveguide, the footprint of the PBS was shrunk to about 2.5 μm × 1.8 μm with using multimode interference [21]. By utilizing the combined hybrid plasmonic waveguide consisting of two Si-SiO 2 -Ag structures, the footprint of the PBS was numerically reduced to about 0.9 μm × 0.9 μm and the bandwidth was up to 400 nm in theory based on the different spatial distributions of the two modes [24]. However, these small PBSs [18][19][20][21][22]24] numerically predicted in the hybrid waveguide structures are difficult to fabricate in the experiment because of the complexity of the hybrid structures.…”

“…By utilizing the combined hybrid plasmonic waveguide consisting of two Si-SiO 2 -Ag structures, the footprint of the PBS was numerically reduced to about 0.9 μm × 0.9 μm and the bandwidth was up to 400 nm in theory based on the different spatial distributions of the two modes [24]. However, these small PBSs [18][19][20][21][22]24] numerically predicted in the hybrid waveguide structures are difficult to fabricate in the experiment because of the complexity of the hybrid structures. To decrease the fabrication difficulty, other mechanisms, such as the resonator effect and the double-slit interference effect, were explored to experimentally realize the PBSs in the planar hybrid air-polymer-metal waveguide structures [25] and the hybrid strip waveguide [26].…”

Fresnel analysis of Kretschmann geometry with a uniaxial crystal layer on a three-layered film

“…The intrinsic characteristics of surface plasmon polaritons (SPP) -strong surface field, effectively short optical wavelength, and directional propagation have led to their application in research on imaging beyond the diffraction limit, 1-3 the capabilities of nano-lithography, 4,5 the implementation of strong surface fields in enhancing fluorescence, 6 second harmonic generation, 7 nano-waveguide routing for signal processing, 8 the design of optical components, 9,10 beam splitters, 11 focusing lenses, 12 metasurface phase manipulations, 13 and holography involving metallic films. 14 The optical tunability of SPP devices depends primarily on the dielectric layer on a structured metallic surface.…”