Simple technique for integrating compact silicon devices within optical fibers

In this work, we present a simple fabrication process enabling the integration of a subwavelength 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 μm) 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°C–400°C. The proposed interferometer is attractive for point monitoring applications as well as for ultrahigh-temperature sensing in harsh environments. © 2014 Optical Society of America OCIS codes: (220.0220) Optical design and fabrication;