Sol-gel processing meets quantum sensing: integrating NV--containing nanodiamonds into a fiber-based magnetic field sensor

Abstract The combination of sol-gel technology with nitrogen vacancy (NV - ) center-containing nanodiamonds (ND) offers a promising platform for the development of thin, functional coatings with magnetically sensitive optical properties. When applied particularly on optical fibers, these hybrid materials enable the creation of compact and highly sensitive magnetic field sensors suitable for both remote sensing and in situ applications. The spatial separation of sensing fiber tip and readout units allows flexible deployment in various magnetic field sensing applications. The developed magnetic field sensor is based on the combination of a stable, chemically resistant sol-gel layer and an embedded ND network with high magnetic sensitivity. In order to achieve homogeneous fixation of the nanodiamonds on the optical fiber, a tailored sol-gel formulation was developed, in which dimethyldiethoxysilane was selectively incorporated to ensure the required flexibility for fiber optic use. The sensor’s performance was evaluated over an operating range of 0–90 mT. It exhibits its greatest sensitivity in the crucial range up to 50 mT, demonstrated by a distinct 15% decrease in photoluminescence intensity in response to the applied magnetic field, after which the signal begins to saturate.