Live cell index sensing based on the reflection mode of tilted fiber tip with gold nanoparticles

We presented a micrometer size tapered fiber tip for real-time refractive index measurement of live cell. The tip is cut with a specific tilted angle. Only the cutting surface of tip apex is coated with gold nanoparticles (GNPs) by selective bonding method. The evanescent wave at the apex will excite the localized surface plasmon resonance (LSPR) of GNPs. With enhanced scattering at the resonance wavelength, the tip reflection will experience a loss, which is analogous to attenuated total reflection (ATR). By measure the reflection beam, a wavelength dependent loss dip in the reflection spectrum or an intensity loss of a specific wavelength could be used to detect the refractive index of live cell.