Simple technique for integrating compact silicon devices within optical fibers

In this work, we present a novel, simple and cost-effective fabrication process, enabling the integration of a sub-wavelength amorphous silicon layer inside optical fibers by means of the arc discharge technique. To assess our method, we have fabricated a compact in line Fabry-Perot interferometer consisting of a thin (< 1 ?m) a-Si:H layer completely embedded within a standard single mode optical fiber. The device exhibits low loss (1.3 dB) and high interference fringe visibility (~80%) both in reflection and transmission, due to the high refractive index contrast between silica and a-Si:H. A high linear temperature sensitivity up to 106 pm/°C is demonstrated in the range 120-400 °C. The proposed interferometer is attractive for point monitoring applications as well as for ultra-high temperature sensing in harsh environments.