Refractive index sensor based on a microhole in single-mode fiber created by the use of femtosecond laser micromachining

Abstract

A compact in-fiber refractive index (RI) sensor is presented that is based on a microhole created in a conventional single-mode fiber by the use of femtosecond laser micromachining. The transmission properties of such a device with a microhole of different diameters have been investigated in the wavelength region of 1500–1600 nm and in the RI range of 1.30–1.45. It is found that the relationship between the transmission and the RI is critically dependent on the size of the microhole in the fiber core region. The highest resolution obtained is $6.70\times {10}^{-5}$, in the RI range of 1.37–1.42, when the microhole diameter is $\sim 8\mu \text{m}$, close to the fiber core size. The in-fiber RI sensor developed in this work is easy to fabricate and can be used to implement temperature-independent measurements.

© 2009 Optical Society of America