Feedback Methods for Vector Measurements Using an All-Optical Atomic Magnetometer.

In this work, we look to compare three methods of feedback for the ultimate purpose of measuring the transverse vector components of a magnetic field using a synchronous light-pulse atomic scalar magnetometer with a few tens of fT/Hz sensitivity in Earth-field-scale magnetic environments. By applying modulation in the magnetic field to orthogonal axes, the respective vector components may, in principle, be separated from the scalar measurement. Success of this technique depends in significant part on the ability to measure and respond to these perturbations with low measurement uncertainty.

All-optical intrinsic atomic gradiometer with sub-20 fT/cm/√Hz sensitivity in a 22 µT earth-scale magnetic field.

In this work we demonstrate a high sensitivity atomic gradiometer capable of operation in earth-field level environments. We apply a light-pulse sequence at four times the Larmor frequency to achieve gradiometer sensitivity <20 fT/cm/H at the finite field strength of 22 µT. The experimental timing sequence can be tuned to the field magnitude of interest.

Characterizing atomic magnetic gradiometers for fetal magnetocardiography.

Atomic magnetometers (AMs) offer many advantages over superconducting quantum interference devices due to, among other things, having comparable sensitivity while not requiring cryogenics. One of the major limitations of AMs is the challenge of configuring them as gradiometers. We report the development of a spin-exchange relaxation free vector atomic magnetic gradiometer with a sensitivity of 3 fT cm Hz and common mode rejection ratio >150 in the band from DC to 100 Hz.

Dual-Axis -Pulse Magnetometer with Suppressed Spin-Exchange Relaxation.

We present a spin-exchange relaxation-free vector magnetometer with suppressed 1 probe noise, achieved by applying a small dc bias field and a comb of magnetic dc pulses along the pump direction. This results in a synchronous orthogonal ac response for each of its two sensitive axes. The magnetometer is particularly well suited to applications such as biomagnetism in which the signal to be measured carries a dominant component of its power at low frequencies.

Synchronous Spin-Exchange Optical Pumping.

We demonstrate a new approach to precision NMR with hyperpolarized gases designed to mitigate NMR shifts due to the alkali spin-exchange field. The NMR bias field is implemented as a sequence of alkali (Rb) 2π pulses, allowing the Rb polarization to be optically pumped transverse to the bias field. When the Rb polarization is modulated at the noble-gas (Xe) NMR resonance, spin-exchange collisions buildup a precessing transverse Xe polarization.