Chemical vapor sensors based on whispering gallery modes in an optical fiber micro-resonator coated with a polymer layer

This study proposes a chemical vapor sensor using whispering gallery modes excited in an optical fiber-based resonator. A standard optical fiber with its plastic buffer removed is coated with a polymer layer to act as the vapor-sensitive optical resonator. Theoretical simulations of the sensor response, including the refractive index sensitivity and detection limit, are performed as a function of the polymer layer thickness. Calculations show that the sensor exhibits a very good linearity and a low detection limit on the order of 10 ⁶ refractive index unit. The theoretical predications also provide guidelines for the design and fabrication of optical fiber-based whispering gallery mode resonators in chemical sensing.