This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers at Fraunhofer IAF have developed a laser-enhanced quantum sensor that combines high magnetic-field sensitivity with a large dynamic range. Using laser threshold magnetometry, they improved the ratio of sensitivity and dynamic range by a factor of up to 590 compared with state-of-the-art approaches.
The breakthrough is enabled by the first demonstration of 100% optical contrast, combined with strong laser readout signals. The results, published in Nature Communications, open up new prospects for medical diagnostics, navigation, and resource exploration. Magnetic-field sensors based on nitrogen-vacancy (NV) centers in diamond are among the leading solid-state quantum sensors.
They operate at room temperature, can be integrated into compact devices and enable vector magnetometry—the measurement of both the magnitude and direction of a magnetic field. Recent advances have improved their sensitivity into the sub-pT/√Hz range, a regime relevant for detecting cardiac signals. Until now, however, researchers have had to make a trade-off: sensors with very high sensitivity offer only a very limited dynamic range, while more robust variants with a large dynamic range were considerably less sensitive.
To address this limitation, researchers at the Fraunhofer Institute for Applied Solid State Physics IAF are pursuing laser threshold magnetometry, an approach that mitigates this trade-off by combining high sensitivity with a large dynamic range. In this approach, NV centers in diamond are directly integrated into a laser cavity as an optical element, where they act as a magnetic-field-dependent loss channel. Rather than measuring the NV fluorescence, the researchers use the system's laser signal as the readout.
The researchers demonstrate such a two-media laser threshold magnetometer. The strong coupling of the NV centers to the cavity field enhances the sensor's response to changes in the magnetic field. The laser system thus achieves 100% optical contrast, rather than the few percent typical for NV magnetometry.
It also delivers a coherent laser readout signal with an output power of up to 50 mW, substantially higher than that of conventional NV-fluorescence readout. If photon shot noise is the dominant noise source, this combination of high contrast and a strong signal yields a sensitivity below 400 fT/√Hz for each of the three components of the magnetic-field vector. The study also provides the first experimental demonstration that the attainable sensitivity improves more than linearly as optical contrast approaches 100%.
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