Arice-sized magnetometer

Can do the job of much bigger units and measure magnetic fields with a sensitivity of 50 picotesla. Researchers at NIST in Boulder, Colorado, exploit the fact that rubidium atoms have quantum levels whose energies depend on the ambient magnetic field. With a rubidium vapor confined in a tiny cell and a precisely tuned laser beam propagating through the cell, the researchers measure the magnetic field by monitoring the absorbed light. The laser, optics, cell, and detector are all fabricated in a 12-mm³ package, about the size of the same group’s atomic clock (see Physics Today, October 2004, page 9 ). What’s more, the device could potentially be manufactured in large batches using wafer-level fabrication techniques. With a few more years of development, the device’s tiny power consumption, compact size, and low price could move it ahead of several existing magnetometer designs for applications like geophysical exploration, medical diagnostics, and detection of underwater or underground iron objects. (P. D. D. Schwindt et al., Appl. Phys. Lett. 85, 6409, 2004 http://dx.doi.org/10.1063/1.1839274 .)