Surface plasmon coupling effects on the fundamental modes in the nanowire

The degeneracy of the two fundamental modes HE₁₁ of the nanowire (NW) is removed due to the coupling of surface plasmon (SP). For the coupled mode 1 of HE₁₁ the electric field is concentrated between the metal sphere and the NW because of the coupling of the metal sphere. The coupling intensity depends on the relative position of the metal sphere. There is no field concentration phenomenon for the coupled mode 2 of HE₁₁, and the coupling only affects the distribution of the local field in the NW. For the coupled mode 2 of HE₁₁, both the mode volume and the Purcell factor do not have obvious change. However, for the coupled mode 1 of HE₁₁ both the mode volume and the Purcell factor have a fundamental change. The mode volume increases with the increase of the metal sphere distance from the point of maximum field intensity of the Fabry-Perot standing wave. The Purcell factor decreases with the increase of the metal sphere distance from the point of maximum field intensity of the Fabry-Perot standing wave.