Spaser based on dark quadrupole surface plasmon mode of a trapezoidal nanoring

摘要

We demonstrate a spaser based on a dark quadrupole surface-plasmon (SP) mode of a trapezoidal nanoring theoretically. The dark quadrupole SP mode can be excited at normal incidence, which is caused by the opposite phase of two different dipoles distributed on the left and right sides of the nanoring. This physical mechanism of the quadrupole SP mode excitation was confirmed by varying the quadrupole SPs as a function of the structural parameters d(s), and h(0), and the trapezoidal nanoring with the same circumference. For the demonstration, we study the properties of the spaser based on the dark quadrupole and bright dipolar SP modes of the trapezoidal ring nanostructure. The dark quadrupole SP mode-based spaser exhibits a lower lasing threshold than the dipole SP mode-based spaser. The lasing wavelength can be tuned over a wide wavelength range. The results should be significant to the development of dark SP mode-based spasers.