The enhancement of the electric field in a hollow metallic cylinder is optimized as a function of the angular frequency of incident light. A resonant enhancement occurs by exciting azimuthal surface plasmon (SP) and the enhancement is uniform inside the cylinder which is useful for spectroscopy. The enhancement of the electric field is numerically calculated by solving the Helmholtz equation as a function of the inner and outer radii of the cylinder from which an empirical formula for the enhancement is obtained by fitting the numerical results. The maximum enhancement occurs near the resonant condition of the SP but it is not exactly at the resonant frequency of the SP. The calculated induced charge density at the inner and outer surfaces show that the maximum enhancement occurs when the induced charge density at the outer surface becomes minimum. We suggest that such suppression of charge density at the outer boundary of the cylinder is the result of the linear combination of two intrinsic modes of the cylindrical SP.

中空金属圆柱体中电场的增强被优化为入射光角频率的函数。通过激发方位表面等离子体 (SP) 发生共振增强，并且增强在圆柱体内是均匀的，这对光谱学很有用。电场的增强是通过将亥姆霍兹方程求解为圆柱的内半径和外半径的函数来进行数值计算的，通过拟合数值结果可以得到增强的经验公式。最大增强发生在 SP 的共振条件附近，但并不完全在 SP 的共振频率处。计算出的内表面和外表面的感应电荷密度表明，当外表面的感应电荷密度变得最小时，出现最大的增强。