Fabrication and thermal characteristics of Ti-Ag-Ni coated regenerated grating sensors for high-temperature sensing

摘要

A regenerated grating (RG) sensor with titanium (Ti) - silver (Ag) - nickel (Ni) multilayer coatings is fabricated by magnetron sputtering and electroplating processes. Optical and thermal testing are performed to evaluate the characteristics of the Ti-Ag-Ni coated RG sensor. The profiles of the reflection spectra of the RG are slightly affected by the metallization process. The shift in the Bragg wavelength of the Ti-Ag-Ni coated RG sensor can be described as a piecewise linear function of temperature, with slope discontinuity at 250 °C. The Ti-Ag-Ni coated RG sensor exhibits more than twice higher sensitivity than that of the bare RG, with satisfactory repeatability and stability at temperatures of up to 600 °C. The surface and cross-section of the sensor are observed with scanning electron microscopy (SEM). The SEM images clear show no discontinuity at the interface between the optical fiber and titanium layer, as well as a good quality of nickel coating without visible dendritic growth. These results indicate that the Ti-Ag-Ni coated RG sensors can be successfully fabricated by combining magnetron sputtering with electroplating, and provide the great potential for high-temperature sensing because of their good sensitivity, repeatability and stability.