Smaller than a grain of sand – 3D-printed quartz glass sensors on glass fibers

For the first time in the communications industry, Swedish researchers have 3D printed fused silica micro-optics onto the tips of optical fibers – surfaces as small as the cross-section of a human hair. This advance could enable faster internet and better connectivity, as well as innovations such as smaller sensors and imaging systems.

The innovative technique overcomes previous challenges in patterning fiber optic tips with silica glass, which often require high temperatures and can compromise the integrity of the temperature-sensitive fiber coatings. Unlike other methods, the process starts with a base material without carbon, eliminating the need for high temperatures to remove carbon and thus produce a transparent glass structure.

According to KTH professor Kristinn Gylfason, the method overcomes the long-standing limitations of patterning glass fiber tips with fused silica, which he says often requires high-temperature treatments that compromise the integrity of the temperature-sensitive fiber coatings.

This advance enables use in environmental and health sensors as well as in pharmaceuticals and chemical production. The researchers demonstrated the application of this technique by printing a silica glass sensor, which proved to be more resistant than conventional plastic sensors.

“We demonstrated a glass refractive index sensor integrated onto the fiber tip that allowed us to measure the concentration of organic solvents. This measurement is challenging for polymer-based sensors due to the corrosiveness of the solvents,” the study’s lead author, Lee-Lun Lai, says.

“These structures are so small you could fit 1,000 of them on the surface of a grain of sand, which is about the size of sensors being used today,” says the study’s co-author, Po-Han Huang. “By bridging the gap between 3D printing and photonics, the implications of this research are far-reaching, with potential applications in microfluidic devices, MEMS accelerometers and fiber-integrated quantum emitters,” he says.

The researchers also demonstrated a technique for printing nanogrids, extremely small patterns that manipulate light in a precise way and could find applications in quantum communication.

The researchers have already applied for a patent for this technique. Their work has far-reaching implications, from microfluidic devices to MEMS acceleration sensors and fiber-integrated quantum emitters, and marks a significant advance in the combination of 3D printing and photonics.