Scientists at RMIT University and the University of Adelaide have developed a diamond sensor using conventional fibers. They embedded μm-scale diamond particles within the cross-section of a silicate glass fiber. The diamond-doped optical fibers drive the fiber optic magnetometry with ensemble nitrogen-vacancy (NV) centers in diamond. The sensor can be used in the field. Diamond containing an NV center is an important platform for quantum sensors, but most NV sensors require microscopes to collect the fluorescence signals. This limits their use to laboratory settings. Heike Ebendorff-Heidepriem at the University of Adelaide said the research team worked to find a way around this issue for a decade. “Because diamond burns at high temperatures, we’ve been limited in the glasses that we can use,” she said. Optic vessels made of glass and diamond by artist Karen Cunningham. Courtesy of Michael Haines Photography. The researchers received inspiration from the work of a local glass blower, Karen Cunningham, who used nanoparticles in her art to show how light moves through glass. “We gave Karen some of our larger diamonds to see how they worked,” RMIT professor Brant Gibson said. “For most of our work, these diamonds are just too big, so we use them mainly for testing.” The diamonds, which were around 1 μm in diameter, survived the high temperatures used in glass blowing. “For us, it was the light bulb moment, and we knew we could make diamond sensors in more conventional glass fibers,” Ebendorff-Heidepriem said. The researchers used luminescence spectroscopy and electron spin resonance characterization to demonstrate that the optical properties of NV centers in the diamond microcrystals used for the sensor were preserved throughout the fiber drawing process. The fiber demonstrated a low propagation loss of about 4.0 dB/m in the NV emission spectral window, permitting remote monitoring of optically detected magnetic resonance signals. The team demonstrated NV-spin magnetic resonance readout through 50 cm of fiber. To go from glass art to prototype sensors took three years of testing and fabrication, the researchers said. The work could open the way for the scalable fabrication of fiber-based diamond sensors for quantum metrology applications that could be deployed underwater, underground, and elsewhere. “It always takes hard work to go from the idea to the product, but I’m so excited by what we’ve achieved, and even more excited by where this new quantum sensor can take us," RMIT researcher Dongbi Bai said. The research was published in APL Materials (www.doi.org/10.1063/5.0013473).