Femtosecond Laser-Inscribed High-Order Bragg Gratings in Large-Diameter Sapphire Fibers for High-Temperature and Strain Sensing

Sapphire fiber Bragg gratings inscribed with a femtosecond laser line-by-line scanning technique

“…Single-crystal sapphire fibers have a high melting temperature of ∼2045°C, and hence could be developed for fabricating various high-temperature sensors [8][9][10][11][12][13][14][15][16][17][18]. Femtosecond laser pulses have been used to inscribe FBGs in sapphire fibers.…”

“…Femtosecond laser pulses have been used to inscribe FBGs in sapphire fibers. To date, three different methods, i.e., the scanning-beam phase mask method [10][11][12][13][14], the Talbot interferometer method [15,16], and the point-by-point inscription method [17,18], have been reported for creating sapphire fiber Bragg gratings (SFBGs). For example, in 2004, Grobnic et al reported for the first time on an FBG inscribed in single-crystal sapphire fiber using an 800 nm femtosecond laser beam through a phase mask [10].…”

“…Moreover, the SFBG with a diameter of 60 μm has a higher reflectivity, a higher SNR, and a narrower bandwidth than the SFBG with a diameter of 100 μm. This may result from a larger number of modes excited in a thicker sapphire fiber [11,14,18]. The SFBG inscribed in the sapphire fiber with a diameter of 60 μm can provide a higher SNR and a narrower bandwidth, which are beneficial for wavelength demodulation.…”

Structural Instability-Enabled Mechanical Sensors Using Fiber Bragg Grating

“…FBG has been reported with promising sensitivity and accuracy for deformation measurement [ 11 , 12 , 13 ]. FBG has been applied in many sensing applications, such as temperature sensors [ 14 , 15 ], acoustic sensors [ 16 ], and stress [ 17 ] or strain [ 18 , 19 , 20 ] sensors. In this study, the FBG observations are compared with predefined thresholds to convert the detected results into binary data.…”

A Temperature Fiber Sensor Based on Tapered Fiber Bragg Grating Fabricated by Femtosecond Laser

“…This inconvenience is challenging to realizing a complex grating structure as well as to expand the practical functions. However, femtosecond laser can remain efficient in fabricating non-photosensitive optical materials, which exhibits obvious advantages in FBG fabrication [18][19][20][21][22]. The femtosecond laser interacts with dielectric material through a high nonlinear photoionization mechanism, leading to the modification which shares no relevance to the photosensitivity of the material [23][24][25][26][27][28].…”