Refractive index sensing with high temperature nano-coated electric arc-induced long-period gratings working at dispersion turning point

The work presents for a first time electric arc-induced long-period gratings (LPGs) working at dispersion turning point (DTP) in wavelength range about 1550 nm. The DTP has been achieved as a result of reduction in grating period down to about 190 μm. In contradiction to LPGs typically fabricated using UV laser-based method, arc-induced gratings show high thermal stability and a great long-term performance. These advantages allow for coating LPG with thin film deposition methods, which require high temperature. We discuss effect of thin silicon nitride (SiN_x) overlay deposition with radio frequency plasma enhanced chemical vapour deposition (RF PECVD) method on refractive index sensitivity of the LPGs.