Modal Analysis and Dispersion Characteristics of a Plasma-Loaded Planar Optical Waveguide

Abstract: A theoretical study of a three-layer plasma-loaded planar optical waveguide is presented. The structure consists of a silica guiding layer, a plasma-filled guiding region, and an air region. The study examines the influence of plasma loading on the effective refractive index and modal dispersion of the planar waveguide. The analysis is based on the phase-matching condition for a three-layer asymmetric slab waveguide, with Transverse Electric (TE) and Transverse Magnetic (TM) polarization effects introduced through the reflection phase shifts at the interfaces. The plasma refractive index is described through the plasma frequency, and the source study considers the normalized plasma-frequency parameter ωp/ω = 0.4. For the numerical investigation, the silica refractive index is taken as 1.40, the air refractive index as 1.00, and the plasma-region width as 2.5 μm. The calculated dispersion curves show distinct mode-dependent variation of effective refractive index with wavelength and plasma-region width. The results demonstrate that plasma loading modifies the modal propagation characteristics and provides a tunable parameter for planar optical-waveguide design.

Keywords: Plasma-loaded waveguide; Planar optical waveguide; Slab waveguide; Effective refractive index; Dispersion; Plasma frequency; TE/TM modes; Propagation constant.