Highly Sensitive Fiber Taper Interferometric Hydrogen Sensors

We report on the implementation of fiber taper interferometric hydrogen sensors with high sensitivity and good reproducibility. The tapering process is carried out with a commercial fusion splicer by precisely controlling the pulling and feeding velocities, as well as arc strength. The taper can naturally act as a Mach-Zehnder interferometer and intrinsically offers a transmission spectrum with periodic interference fringes. The sensor with a waist diameter of 3.0 mu m can present a spectral shift up to -1.99 nm when injecting hydrogen with a concentration of 5% as a result of strong evanescent field interaction with the Palladium overlay. We have fabricated a number of sensors with identical parameters and found that the relative error ratio in waist diameter is less than 6% and that in hydrogen response is 4.2%.