LAUSR

Abstract The optical properties of compact in-fiber refractive index (RI) sensor based on a micro-hole created in a conventional single-mode fiber using femtosecond laser micromachining is further investigated. It is found that the well-controlled lateral-offset of the micro-hole could increase the sensitivity of the sensor. This is followed by an experiment observing the influence of micro-hole diameter and lateral-offset on the transmission intensity response to fluid which RI ranges from 1.33 to 1.45. Numerical and experiment results show that the RI turning point of such sensor is largely determined by micro-hole diameter, and the sensitivity is closely related to the lateral-offset. To achieve high sensitivity, the micro-hole diameter and the lateral-offset should be adjusted to match the RI of the fluid. Both cylinder and taper micro-hole types are considered, and the numerical simulation agrees well with relevant experiment.