A thousand times smaller than a grain of sand—glass sensors 3D-printed on optical fiber

In a first for communications, researchers in Sweden 3D printed silica glass micro-optics on the tips of optic fibers—surfaces as small as the cross section of a human hair. The advance could enable faster internet and improved connectivity, as well as innovations like smaller sensors and imaging systems.

Reporting in the journal ACS Nano, researchers at KTH Royal Institute of Technology in Stockholm say integrating silica glass optical devices with optical fibers enables multiple innovations, including more sensitive remote sensors for environment and health care.

The printing techniques they report also could prove valuable in production of pharmaceuticals and chemicals.

KTH Professor Kristinn Gylfason says the method overcomes longstanding limitations in structuring optical fiber tips with silica glass, which he says often require high-temperature treatments that compromise the integrity of temperature-sensitive fiber coatings.

In contrast to other methods, the process begins with a base material that doesn't contain carbon. That means high temperatures are not needed to drive out carbon in order to make the glass structure transparent.

The study's lead author, Lee-Lun Lai, says the researchers printed a silica glass sensor that proved more resilient than a standard plastic-based sensor after multiple measurements.

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"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," 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.

The researchers also demonstrated a technique for printing nanogratings, ultra-small patterns etched onto surfaces at the nanometer scale. These are used to manipulate light in precise ways and have potential applications in quantum communication.

Gylfason says the ability to 3D print arbitrary glass structures directly on fiber tip opens new frontiers in photonics. "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.