We present a theoretical analysis of the refractometric sensitivity of a spherical microresonator coated with a porous sensing layer performed for different whispering gallery modes. The effective refractive index of the modes is also calculated. The calculations are also made for a system which has an additional high-refractive index layer sandwiched between the microsphere and the porous sensing layer. The results of the calculation are discussed in regards to the applicability of the studied systems for gas sensor construction.
Keywords: microspheres; refractometric sensing; whispering gallery modes.