Reviewed by Danielle Ellis, B.Sc.Oct 9 2024
Researchers from Fraunhofer IAF have now successfully demonstrated the sensor system with two active media for the first time by combining an NV diamond and a laser diode in a resonator, as reported in a study published in Science Advances.
Lukas Lindner and more researchers have successfully demonstrated the dual NV diamond laser system for the first time and published the results in the journal Science Advances. Image Credit: Fraunhofer IAF
Numerous new and innovative possibilities for medical diagnosis and treatment are made possible by the measurement of minute magnetic fields, such as those produced by brain waves. The Fraunhofer IAF research team, under the direction of Dr. Jan Jeske, is developing Laser Threshold Magnetometry, a globally novel method for accurate magnetic field measurements.
This excellent study marks a major advancement in the NeuroQ research project, which is funded by the BMBF.
For accurate magnetic field measurements at room temperature and in background magnetic fields, quantum sensors based on nitrogen-vacancy (NV) centers in diamond are already in widespread use. A new research method for measuring extremely low magnetic fields in the femtotesla (fT) to picotesla (pT) range is called laser threshold magnetometry (LTM).
Furthermore, LTM eliminates the need to suppress background fields, enabling measurements with a high dynamic range. For medical applications like measuring biomagnetic signals from the heart or brain, these characteristics make laser threshold magnetometry especially helpful.
Laser Threshold Magnetometry Principle
The scientific principle of LTM has already been thoroughly investigated in theory. Since then, researchers at the Fraunhofer Institute for Applied Solid State Physics (IAF) have been working on developing the first laser threshold magnetometer. The basic idea is to create a laser from NV centers and then use the laser light, which reacts to magnetic fields, to get precise information about the strength and direction of a magnetic field.
The point at which the laser begins or ceases to emit light is known as the laser threshold. Magnetic fields can be measured very precisely at the laser threshold because they have a very strong effect on the signal. Laser signals can be measured over a larger dynamic range and with far greater accuracy than fluorescent light.
In 2022, the first magnetic field-dependent light amplification of NV centers was successfully demonstrated by researchers at Fraunhofer IAF. However, the laser threshold of the NV centers could not yet be achieved because of the external laser source.
First Demonstration of the Laser Threshold
In the current study, the researchers combined NV diamond with a second laser medium, a laser diode, to increase light amplification in an optical resonator. This allowed them to demonstrate the laser threshold for the first time: depending on how strongly the NV centers were pumped, the laser system would turn on or off.
The results are a breakthrough for the development of laser threshold magnetometry. On this basis, sensors with up to 100 percent contrast, strong light signals and a wide range of measurable magnetic field strengths can be realized in the future.
Dr. Jan Jeske, Researcher, Fraunhofer IAF
An early version of the lighthouse project "Laser threshold magnetometer for neuronal communication interfaces," or NeuroQ for short, which is supported by the German Federal Ministry of Education and Research (BMBF), is displayed in the work of first author Lukas Lindner. The NeuroQ project team is now working on improving the sensitivity and further developing the novel NV diamond laser system, which is presently undergoing the patent application process.
The BMBF Lighthouse Project NeuroQ
High-precision quantum sensors for medical applications are being developed by the NeuroQ consortium, which includes Fraunhofer IAF, Charité - Universitätsmedizin Berlin, University of Stuttgart, and additional industrial partners: Through a brain-computer interface, the quantum sensors will measure neuronal activity and send the signals to an exoskeleton. Through the use of this technology, paralyzed individuals will be able to regain some degree of mobility by using their thoughts to control an exoskeleton.
Journal Reference:
Lindner, L. et. al. (2024) Dual-media laser system: Nitrogen vacancy diamond and red semiconductor laser. Science Advances. doi.org/10.1126/sciadv.adj3933