Mid-infrared chirped fiber Bragg gratings inscribed in fluorotellurite fiber using a femtosecond laser

In this paper, chirped fiber Bragg gratings (CFBGs) with tunable parameters are successfully fabricated in fluorotellurite fiber (FTF) using the femtosecond laser point-by-point method combined with slit beam shaping technique. By precisely controlling the processing parameters, CFBGs with adjustable bandwidths (3-9 nm) and center wavelengths (3.5-3.7 μm) are realized, and the highest reflectivity is 99%. The fabricated CFBGs demonstrate good temperature response characteristics from room temperature to 400°C, with a temperature sensitivity of 39.47 pm/°C. This study first achieves flexible fabrication of mid-infrared CFBGs in FTF using the femtosecond laser point-by-point method, providing critical device support for the development of mid-infrared fiber lasers and demonstrating significant application value.