Long-range surface plasmon-polariton mode cutoff and radiation

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Abstract
Using a fully vectorial formulation, the normal mode analysis method is used to model the radiative spreading of surface plasmon-polariton modes input into regions where the bound surface mode is cutoff, or radiative. The analysis was performed at λ 0 = 1.55 μ m for embedded finite-width metalwaveguides where the metal was Au and the surrounding dielectric was SiO 2 . Mode cutoff is induced by an asymmetry between the index of refraction of the top clad and the bottom clad. Results show that a change in insertion loss of better than 20 dB is possible for an appropriate waveguide and dielectric asymmetry. Comparisons between predictions and experimental results show very good agreement.