Hybrid plasmonic bottle microresonators

Hybrid plasmonic bottle microresonators (PBMR) have been demonstrated to sustain polarization dependent surface plasmon waves (SPWs). The proposed PBMR was fabricated by depositing thin gold film on one side of a standard BMR. The deposited gold film has a characteristic meniscus shape with 30 nm maximum thickness. The meniscus provides appropriately tapered edges which facilitate low-loss adiabatic transformation of BMR WGMs to SPWs and vice versa. Microtaper fiber TE and TM evanescent field excitations from the uncoated part of the PBMR were observed to generate composite resonances with Q of ~ 2100 and ~ 850, respectively. Lorentzian fitting of the measured data reveals that the TE and TM excitations are actually composite resonances consisting of two and three partially overlapping resonances with Qs in excess of 2900 and 2500, respectively and almost identical FSR of ~ 3 nm. This is the highest individual plasmonic Q ever reported in any plasmonic cavity to date. Numerical modelling of the hybrid PBMR reveals the nature of the excited waves.