Bell&Bloom

The activity of our laboratory started about 25 years ago thanks to a project aimed to develop optical magnetometers. The research about atomic magnetometry triggered several activities both oriented to application and to study physical phenomena related to that subject (and not only). 

Among the most sensitive methods of measuring magnetic fields, atomic magnetometry is based on the interaction of resonant light with an atomic sample, typically a thermal vapour. Recent developments in this research have led to improvements in the performance of atomic magnetometers. The availability of advanced light sources, light detectors, fiber-coupled devices, DAQs etc. made atomic magnetometers flexible, versatile and relatively cheap. They can compete with SQUIDs that use another working principle and represent the current state-of-the-art magnetic sensors. Compared to SQUIDs, atomic magnetometers present the advantage of not requiring bulky cryogenics.

Atomic magnetometers are currently used worldwide to detect biomagnetic fields, to visualize magnetically marked materials (including biological tissues), to record NMR and MRI signals in unconventional (vanishing fields) conditions. They are also employed in inertial rotation sensing, in magnetic microscopy, in detecting magneto-nano-particles, in testing fundamental symmetries.

There exists a variety of families and arrangements of atomic magnetometers. The device developed in our lab uses a light-modulated optical pumping (in the so-called Bell&Bloom configuration) and a dual-cell, dual-color setup. The dual-cell enables magnetic disturbance rejection by means of differential measurement. The dual-color arrangement permits to filter out the pumping radiation (D1 Cs line) while polarimetrically analyzing the probe one (tuned to the D2 Cs line).

We are interested both in developing the magnetometer and in the improvement/characterization of its performance. At the same time we consider the application of atomic magnetometry in challenging measurements, such as in magnetocardiography, in ultra-low-field NMR and MRI. Our efforts aim to make the system work in an unshielded environment, and to this end we perfected advanced field-stabilization methods, and peculiar differential detection schemes.

We are also interested in studying and applying peculiar phenomena that occur when the atomic sensor is merged in a magnetic field that has a fast time-dependence. In particular, we developed and studied new schemes of a phenomenon known as "magnetic-dressing". The magnetic dressing led us to develop original, complex field configurations, as well as to demonstrate promising applications, e.g. in ULF-MRI and in MIT (magnetic induction tomography).