Laser writes 3-D Bragg sensor network within bulk glass

The use of individual Bragg grating or long-period grating structures for sensing temperature, strain, refractive index, and other physical or chemical parameters in their vicinity is well known (see www.

The use of individual Bragg grating or long-period grating structures for sensing temperature, strain, refractive index, and other physical or chemical parameters in their vicinity is well known (see www.laserfocusworld.com/articles/330756). Up until now, the use of such sensors over a broad area or along a length required multiplexing of individual sensors, increasing insertion loss and reducing sensitivity of the overall joined structure. But that was before researchers at the University of Toronto (Toronto, ON, Canada) learned how to create a three-dimensional distributed network of optical sensors within bulk glass with sensing performance similar to traditional fiber Bragg grating (FBG) devices, and can withstand temperatures of up to 750°Cwell beyond conventional FBGs.

A sensing network was fabricated in 50 × 50 × 1 mm3 fused-silica glass by writing waveguides using a 522 nm, 300 fs pulse duration, 500 kHz repetition-rate, modulated ultrafast laser. The writing process uses the laser bursts to create a series of two columns and two rows of cascaded refractive-index voxel segments written 75 µm above and below the glass surface, dividing it into nine sensing zones that were butt-coupled to optical fibers. By sending broadband light through the fibers, shifts in the reflected spectrum at each of the zones can be used to determine strain, temperature, and other parameters individually for each of the 3-D distributed sensing regions. Contact Haibin Zhang at haibin.zhan

More in Fiber Optics