Spectral Features of Tilted Fiber Bragg Gratings Inscribed With Femtosecond-Pulse Laser Radiation

This article reports on the results of an experimental study concerning the spectral features of tilted fiber Bragg gratings (TFBGs) inscribed with femtosecond radiation. The grating samples were fabricated by exposing the fiber core to the femtosecond laser radiation using the core-scanning technique. A comparative analysis was conducted to evaluate the spectral characteristics of femtosecond- and ultraviolet-incribed samples. A number of characteristic properties of femtosecond gratings were discovered, differentiating them from ultraviolet-inscribed tilted gratings, and the explanation for the observed phenomena was provided. Of greatest interest is the significantly larger width of the signal spectrum’s envelope and the short-wavelength region spectral cutoff, which allows the use of femtosecond tilted gratings as the basis for fiber refractometers with an extended sensing range, reaching the levels of gas refractive index sensing.