Efficient energy transfer of a nanodot coupler with resonant light scattering of metallic nanoparticles

Abstract

To realize a nanometer-scale optical waveguide for far-/near-field conversion, we proposed a nanodot coupler which is the linear array of closely spaced metallic nanoprticles in order to transmit the optical signal to a nanophotonic device. In comparison with metallic core waveguide, the use of nano-dot coupler is expected to realize lower energy loss due to the resonant in the metallic nanoparticles. First, to optimize the efficiency in the nanodot coupler, we checked whether the single Au nanoparticles led to efficient scattering. The Au nanoparticles on the glass substrate were fabricated by the focused ion beam milling technique. The optical near-field intensity for the Au nanoparticles in diameter range from 100 to 300nm with constant height of 50nm were observed by the collection mode near-field optical microscope (NOM) at λ = 785nm. Near-field intensity took the maximum for the Au nanoparticle with 200nm in diameter, and this result is in good agreement with the calculated value of plasmon resonance by Mie's theory for an Au prolate spheroid. Next, we examined the plasmon-polariton transfer of nanodot couplers whose diameter range from 150 to 300nm by the collection mode NOM. The efficient energy transfer was observed only in the nanodot coupler with 200nm in diameter. This result agreed well with that of single Au nanoparticles. From these results, efficient energy transfer along nanodot coupler was confirmed by the near-field coupling between plasmon-polariton in the nanoparticles.