Title :
A two-color pump probe atomic magnetometer for magnetoencephalography
Author :
Johnson, Cort ; Schwindt, Peter D.D.
Author_Institution :
Sandia Nat. Labs., Albuquerque, NM, USA
Abstract :
In recent years, atomic magnetometers (AMs) have demonstrated sub-femtotesla sensitivities and have emerged as potential replacements for superconducting quantum interference devices (SQUIDs). In an AM, a circularly polarized pump laser aligns the electron spins in a cloud of alkali metal vapor. Changes occur in the optical properties of the vapor when its collective moment interacts with an external magnetic field, resulting in a measurable polarization rotation of a linearly polarized probe beam. We present a unique pump/probe scheme in which a pump beam tuned to the 87Rb D1 line (795 nm) and a probe beam tuned to the D2 line (780 nm) share a single optical axis. A dichroic waveplate is used to circularly polarize the pump beam while leaving the probe beam linearly polarized. Based upon this scheme, we have developed a small profile, fiber-coupled AM. By independently optimizing pump/probe power and detuning, we are able to achieve intrinsic single-channel sensitivity of <; 5 fT/√Hz, which is suitable for demanding applications such as magnetoencephalography (MEG). Furthermore, through straightforward adaptations of the current design, it should be possible to create dense, reconfigurable arrays of AMs for whole-head MEG.
Keywords :
SQUID magnetometers; magnetoencephalography; SQUID; alkali metal vapor; circularly polarized pump laser; intrinsic single-channel sensitivity; linearly polarized probe beam; magnetoencephalography; optical properties; polarization rotation; probe beam; subfemtotesla sensitivities; superconducting quantum interference devices; two-color pump probe atomic magnetometer; Laser beams; Laser excitation; Magnetic noise; Magnetic resonance; Magnetometers; Probes; Sensitivity;
Conference_Titel :
Frequency Control Symposium (FCS), 2010 IEEE International
Conference_Location :
Newport Beach, CA
Print_ISBN :
978-1-4244-6399-2
DOI :
10.1109/FREQ.2010.5556310