Whispering gallery mode resonators coated with Au nanoparticles

Whispering gallery mode resonators (WGMRs) are very interesting for sensing because a resonance shift could be caused by any perturbation of the surrounding environment. Additionally such a resonator is coated with nanomaterials to tailor and enhance the sensitivity for a specific purpose. WGMR were fabricated using standard telecommunication fiber and a hydrogen flame, characterized using the scan method to obtain the quality factors and then coated with gold nanoparticles (Au NPs) using dip coating method and characterized again for comparison. Au NPs were chosen because their positive impact on microresonator sensitivity has been mentioned before and the surface can later be functionalized. The deposited layer was investigated and new properties no over-coupling due to Van der Waals forces and suppression of higher order modes were observed after coating the resonator. To observe the localized surface plasmon resonance a glucose sensor test was performed using the WGMRs coated with Au NPs and glucose oxidase. Comparing the results with control measurements, the resonance shifted more for samples with Au NPs.