Effective index analysis of bowtie aperture plasmonic waveguides via TM–TE mode decomposition
| dc.contributor.author | Nagi, Udhav | |
| dc.contributor.supervisor | Gordon, Reuven | |
| dc.date.accessioned | 2025-12-16T16:09:53Z | |
| dc.date.available | 2025-12-16T16:09:53Z | |
| dc.date.issued | 2025 | |
| dc.degree.department | Department of Electrical and Computer Engineering | |
| dc.degree.level | Master of Engineering MEng | |
| dc.description.abstract | A Modified Effective Index Method (MEIM) is presented for determining the propagation constant of nanoscale bowtie aperture waveguides operating across the 𝟓𝟎𝟎 − 𝟏𝟎𝟎𝟎 𝒏𝒎 spectral range. The approach uses staircase discretization to approximate the tapered bowtie geometry and employs a geometry-driven formulation to maintain numerical stability for sub-𝟑𝟎 𝒏𝒎 features. The transverse-magnetic (TM) response is computed using the hyperbolic-tangent dispersion relation for a three-layer metal–insulator–metal (MIM) stack, while the transverse-electric (TE) contribution is incorporated using a multi-slab transfer-matrix method (TMM) that enforces field continuity across discretized slabs. By combining these formulations, the model reproduces the expected plasmonic behaviour, including a monotonic decrease in effective index with increasing wavelength and stronger confinement for smaller bowtie gaps. Using wavelength-dependent Silver permittivity data, the MEIM results agree well with the rectangular-slab reference problem, confirming the correctness of both the TM and TE formulations. The framework remains computationally efficient, physically interpretable, and easily extendable to other subwavelength apertures, offering a useful preliminary design tool for plasmonic waveguides and sensing structures. | |
| dc.description.scholarlevel | Graduate | |
| dc.identifier.uri | https://hdl.handle.net/1828/22992 | |
| dc.language.iso | en | |
| dc.subject | Effective Index Method | |
| dc.subject | propagation constant | |
| dc.subject | bowtie aperture waveguide | |
| dc.subject | geometry-driven | |
| dc.subject | sub-30 nm features | |
| dc.subject | metal-insulator-metal | |
| dc.subject | transfer-matrix method | |
| dc.title | Effective index analysis of bowtie aperture plasmonic waveguides via TM–TE mode decomposition | |
| dc.type | project |