Spheroidal particle plasmons in amplifying media

摘要

The effect of a surrounding gain medium on the localized surface plasmon resonance in spheroidal metal particles is analyzed in the quasi-static limit of the Maxwell equations. It is shown that the gain required to create a singularity in the dynamic polarizability of the particle is significantly lower for non-spherical spheroids than for spheres, and can be as low as several hundred inverse centimeters for noble metals in the near infrared region of the spectrum. Resonant aspect ratios and gain values are calculated as a function of frequency for various metals. The use of non-spherically shaped nano-particles, along with gains achievable in semiconductors and dyes, can result in surface enhanced Raman scattering (SERS) signals which are dramatically enhanced.