Ultrahigh Sensitivity Refractive Index Sensor Based on Optical Microfiber

We demonstrate a nonadiabatic microfiber sensor with a taper diameter of few micrometers. The modal interference caused by the abrupt taper results in a sinusoidal spectral response. The wavelength shift arising because of the changes in the external refractive index is found to be significant, achieving a maximum sensitivity of 18681.82 nm/RIU. The measured results show good agreement with the theoretical predictions. The high sensitivity and the simplicity offer the sensor the potential for many real applications.