Optimizing Nano-Optical Antenna for the Enhancement of Spontaneous Emission

We study the characteristics of nano-optical antenna made of two gold nano-particles by three dimensional numerical calculations in visible and near infrared bands. To carry the computational burden and guarantee the precision and speed of a three dimensional FDTD calculation, adaptive mesh refinement technology is used. In this paper, we first highlight the concrete way of controlling the emitter position and orientation to fulfill the requirements of larger spontaneous emission enhancement. Then, we analyze the far field distribution and find that the far fied directivity is strongly influenced by surface plasmon polaritons (SPPs). Choosing the incident wavelength of 600 nm, we compute the decay rates and radiant efficiency as a function of antenna geometry limitations. Next, the particle aspect ratio is optimized, and we obtain that / = 4 is the best for our optical-antenna. Furthermore, we present a spectrum analysis. Around 5000 fold spontaneous emission enhancement is successfully achieved. Finally, we find a piecewise linearity relationship between the particle length and resonant wavelength.