COSMA: Coherent Optics Sensors for Medical Application is an European Marie Curie Project running from 2012 to March 2016, with the participation of 10 teams from Armenia, Bulgaria, India, Israel, Italy, Poland, Russia, UK, USA. The main objective was to focus theoretical and experimental research on biomagnetism phenomena, with the specific aim to develop all-optical sensors dedicated to their detection and suitable for applications in clinical diagnostics. The paper presents some of the most recent results obtained during the exchange visits of the involved scientists, after an introduction about the phenomenon which is the pillar of this kind of research and of many other new fields in laser spectroscopy, atomic physics, and quantum optics: the dark resonance.
We describe our investigations aiming at the detection of the Bloch–Siegert effect (BSE) with nonlinear magneto– optical effects. Although theoretical aspects of the BSE were thoroughly investigated, there are still open questions concerning experimental demonstration of the effect. The most recent BSE experiment was performed in alkali–metal vapor, where atoms were pumped by electron collisions, but the results of those investigations were rather inconclusive. Here we propose to search for the BSE with optically pumped magnetometers (OPMs) and describe the preparation of a dedicated setup providing improved capabilities for observation of the effect in atomic vapor. As the main difficulty is the weakness of the effect and presence of other competing processes, we concentrate on identification and assessment of various systematic effects that may imitate and/or perturb the investigated effect.