Femtosecond laser induced microfiber Bragg grating for refractive index sensing

Fiber Bragg grating (FBG) is fabricated in the microfiber by use of femtosecond laser pulse irradiation. Such a grating can be directly exposed to the surrounding medium without etching or thinning treatment of the fiber, thus possessing high refractive index sensitivity while maintaining superior reliability. The FBG was successfully inscribed on the tapered fiber with diameters ringing from 2 to 10 μm. Such a grating has high potential in various types of optical fiber sensor applications.