# A microfabricated optically-pumped magnetic gradiometer

## TL;DR

This paper introduces a microfabricated atomic magnetic gradiometer capable of detecting minute magnetic field differences with high sensitivity and noise rejection, suitable for applications needing precise gradient measurements.

## Contribution

The development of a compact, chip-scale atomic magnetic gradiometer operating in the spin-exchange relaxation free regime with high sensitivity and noise rejection capabilities.

## Key findings

- Detects magnetic field differences of 10 fT/Hz$^{1/2}$ at >20 Hz
- Achieves 1000-fold magnetic noise rejection at 10 Hz
- Operates effectively with external bias fields up to 150 mG

## Abstract

We report on the development of a microfabricated atomic magnetic gradiometer based on optical spectroscopy of alkali atoms in the vapor phase. The gradiometer, which operates in the spin-exchange relaxation free regime, has a length of 60 mm and cross sectional diameter of 12 mm, and consists of two chip-scale atomic magnetometers which are interrogated by a common laser light. The sensor can measure differences in magnetic fields, over a 20 mm baseline, of 10 fT/Hz$^{1/2}$ at frequencies above 20 Hz. The maximum rejection of magnetic field noise is 1000 at 10 Hz. By use of a set of compensation coils wrapped around the sensor, we also measure the sensor sensitivity at several external bias field strengths up to 150 mG. This device is useful for applications that require both sensitive gradient field information and high common-mode noise cancellation.