Fabrication of periodic structures in optical fibers by femtosecond laser micromachining for sensing applications

Abstract

A femtosecond laser direct writing system was developed to explore the fabrication of periodic structures in optical fibers. The possibility to write type I first- A nd second-order Bragg gratings in the same single-mode fiber (SMF-28e), with reflectivities of 99.6 % and 59.3 %, respectively, is presented. The fabrication of structures (waveguides and grating) in a coreless and in a SMF-28e fiber was first demonstrated, and the gratings were then exposed to a thermal annealing up to 1000°C. The FBG inscribed in the SMF-28e fiber presents thermal stability at temperatures of 800 °C and a temperature sensitivity of 14.34 pm/°C was determined. © 2019 SPIE.