Fabrication of Bragg gratings in flat silica substrates using the FEMTOprint device and use for sensing

Femtosecond laser-based 3D printing has strongly improved the field of photonics, enabling the fabrication of complex optical components. In this study, we present the development and characterization of a bulk Bragg grating sensor created using the FEMTOprint system, which integrates a femtosecond laser for high-precision structuring. The latter enables the direct writing of waveguides with Bragg gratings within a transparent substrate. This unique manufacturing process grants control over the waveguide's geometry, grating period, and refractive index modulation, resulting in sensor capable of extraordinary sensitivity. We conducted a characterization of the waveguide with a Bragg grating sensor to assess its performance. Our results demonstrate remarkable sensitivity to environmental parameters, with a temperature sensitivity of 10.51 pm/°C and a mechanical strain sensitivity of 1.22 pm/με. These characteristics make the sensor ideal for a wide range of applications, including temperature monitoring and structural health assessment. The innovative combination of femtosecond laser printing and Bragg grating technology offers a new dimension to the design and application of optical sensors. Our research not only highlights the unique capabilities of these sensors but also opens up exciting prospects for future developments and interdisciplinary collaborations.