Femtotesla atomic magnetometer with counter-propagating optical sideband pumping

Area of Science:

• Atomic physics
• Quantum sensing
• Magnetometry

Background:

• Spin-exchange relaxation-free (SERF) atomic magnetometers achieve fT/Hz^1/2 sensitivity.
• Gradiometer configurations enhance sensitivity by canceling common-mode noise.
• Channel imbalances due to pump beam attenuation limit gradiometer performance.

Purpose of the Study:

• To develop a novel optical pumping method to equalize channel responses in SERF atomic magnetometer gradiometers.
• To reduce undesirable optical pumping effects like light shifts and polarization inhomogeneity.
• To achieve high sensitivity and spatial resolution in atomic magnetometer arrays.

Main Methods:

• Proposed a counter-propagating optical sideband pumping method.
• Utilized an electro-optic modulator to generate red- and blue-detuned sidebands from a single pump beam.
• Constructed a gradiometer atomic magnetometer using this pumping scheme.

Main Results:

• Achieved a magnetic field sensitivity of 0.5 fT/Hz^1/2 in the 5–40 Hz range.
• Demonstrated equal magnetic response between the two gradiometer channels.
• Significantly reduced light shifts and spatial inhomogeneity in atomic spin polarization.

Conclusions:

• The counter-propagating optical sideband pumping method effectively equalizes channel responses in atomic magnetometer gradiometers.
• This technique enables the development of highly sensitive and spatially resolved atomic magnetometer arrays.
• Potential applications include advanced magnetocardiography/magnetoencephalography imaging and searches for exotic spin interactions.