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Magneto-optical metrology

Working group 8.21

Optically pumped magnetometers

In optically pumped magnetometers, gaseous atoms are used as sensitive magnetic field probes. For this purpose, the quantum-mechanical state of the atoms is prepared by using laser light and the effect of a magnetic field on this state is read out by laser light. During the preparation, the spins of the atoms in a gas cell are "pumped" into a certain spin state and driven to a coherent rotation. In a magnetic field, the spins then precess collectively with the lamor frequency which is proportional to the magnetic flux density. This effect on the quantum-mechanical state of the atoms is subsequently read out by means of laser-spectroscopic methods.

OPMs have rapidly developed in the past two decades and now reach sensitivities like those of SQUIDs. Evaporated alkaline metals such as potassium, rubidium or cesium serve as gaseous atoms. Therefore, no cryogenic temperatures are necessary and the sensors can ultimately be small and flexible.

The goal of the group is the further development of OPMs to use these devices in new fields of application in medical physics (e.g. detection and imaging of magnetic nanoparticles) and in the field of fundamental physics.

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