ENHANCED SENSITIVITY OF A WHISPERING GALLERY MODE MICROSPHERE SENSOR BY A HIGH-REFRACTIVE INDEX SURFACE LAYER

摘要

The use of whispering gallery mode (WGM) evanescent waves to detect adsorption of molecules to the surface of microsphere sensors and more particularly to the utilization of a high refractive index surface layer to increase the sensitivity thereof. The present invention examines the sensor capability of WGM in a dielectric sphere coated with a thin uniform dielectric layer of a high refractive index. Among the utilities of such a modified resonator for the sensing are to have an evanescent field of a different penetration depth without using a non-silica based microsphere or changing the laser wavelength, to further enhance the sensitivity by drawing the optical field of WGM into the coating layer, and to realize the same relative shifts for WGM of different radial modes, thus eliminating ambiguities in the measurement of a refractive index change in the surrounding medium.