  We have investigated the unique effects of metallic nanoparticle on the ring
resonator, especially multiple Au nanoparticles on the micro ring resonator
with the 4-port configuration on chip. For the Au nanoparticle, because it has
smaller real refractive index than air and large absorption refractive index,
we found that there is a blue shift for the ring resonance wavelength, instead
of red shift normally observed for dielectric nanoparticles. The drop port
intensity is strongly dependent on both number and size of nanoparticles, while
relatively independent on position of nanoparticles. The correlation between
the penetration depth of Au and the resonance mode evanescent tail is also
discussed to reveal the unique properties of Au nanoparticle to be used for
detection, sensing and nano medicine.
