Refractive index sensor based on gold coated whispering gallery mode microdisk resonator

Refractive index (RI) sensors based on whispering gallery mode microdisk resonator with creasent-shape and full gold layer coating are numerically investigated. Benefit from the surface plasmon polaritions (SPPs) induced by gold coating, the crescent-shaped and fully gold-coated microresonators reveal sensitivity increasement of up to 31.8% and 81.1% over the resonator without gold coating, respectively. The extinction ratio of crescent-shaped gold-coated microresonator is demonstrated to be adjusted by changing the coupling distance. Furthermore, a maximum surface energy enhancement of up to 83.3% is obtained for microresonator with a full gold coating.