Femtosecond laser fabrication of nanograting-based distributed fiber sensors for extreme environmental applications

The femtosecond laser has emerged as a powerful tool for micro- and nanoscale device fabrication. Through nonlinear ionization processes, nanometer-sized material modifications can be inscribed in transparent materials for device fabrication. This paper describes femtosecond precision inscription of nanograting in silica fiber cores to form both distributed and point fiber sensors for sensing applications in extreme environmental conditions. Through the use of scanning electron microscope imaging and laser processing optimization, high-temperature stable, Type II femtosecond laser modifications were continuously inscribed, point by point, with only an insertion loss at 1 dB m(-1) or 0.001 dB per point sensor device. High-temperature performance of fiber sensors was tested at 1000 degrees C, which showed a temperature fluctuation of +/- 5.5 degrees C over 5 days. The low laser-induced insertion loss in optical fibers enabled the fabrication of a 1.4 m, radiation-resilient distributed fiber sensor. The in-pile testing of the distributed fiber sensor further showed that fiber sensors can execute stable and distributed temperature measurements in extreme radiation environments. Overall, this paper demonstrates that femtosecond-laser-fabricated fiber sensors are suitable measurement devices for applications in extreme environments.

Automated summary

This paper discusses the precision inscription of nanogratings in silica fiber cores using femtosecond lasers for device fabrication and sensing applications in extreme environmental conditions. The high-temperature stable and low insertion loss sensors were continuously inscribed point by point, showing stable and distributed temperature measurements in extreme radiation environments. The femtosecond-laser-fabricated fiber sensors have been proven suitable measurement devices for applications in extreme environments.