Chip-Scale Atomic Magnetometer

NEW ENABLING TECHNOLOGY

Credit: NIST

Measurement of faint magnetic fields is critical to many applications, notably including medical diagnostics, but conventional technologies are often large, complex and expensive. 

NIST’s chip-scale atomic magnetometer, by contrast, is highly compact and readily fabricated using familiar semiconductor techniques. It employs small beams of circularly polarized laser light passing through a millimeter-sized chamber containing a vapor of alkali atoms. The presence of a magnetic field alters the spin orientation of the atoms; that in turn changes the polarization of the outgoing laser beam, which is detected optically. The magnitude of the change is a sensitive measure of field strength.

SMALL SIZE AND POWER REQUIREMENTS; MANUFACTURABLE BY EXISTING SEMICONDUCTOR TECHNIQUES

Diagnosis with magnetometers can detect fields caused by electrical currents in the brain and heart that are predictive of epilepsy, cardiac dysfunction and other conditions. For the brain, conventional technologies employed are electroencephalography, in which electrodes are placed directly on the patient’s skull, and magnetoencephalography in which superconducting sensors called SQUIDs are cooled to 4 degrees above absolute zero and placed at some distance above the skull. Magnetic fields from brain waves, which are feeble to begin with, decrease with distance to the sensor.

The NIST chip-scale magnetometer operates slightly above room temperature and does not directly touch the skull. It is also completely passive, sensing the brain fields without disturbing the brain in any way.