Enhancing sensitivity of a whispering gallery mode biosensor by subwavelength confinement
O. Gaathon, J. Culic-Viskota, M. Mihnev, I. Teraoka, and S. Arnold
Appl. Phys. Lett. 89, 223901 (2006)

The authors demonstrate enhanced sensitivity of a spherical whispering gallery mode biosensor
WGMB by confining orbiting light near the surface using a subwavelength sub- high refractive
index layer on a fluorine doped silica microsphere radius R 200 m . Their experiments at a free
space wavelength 1310 nm show that the frequency shift sensitivity by changing the external
refractive index is increased by more than 700% by adding a 340 nm thick polystyrene layer. This
advance is expected to move the WGMB well into the lead as the most sensitive method for
unlabeled biosensing.