Measuring magnetic fields with accuracy is important, whether it's for geological exploration or medical imaging. Now, a team from MIT has developed a new laser-based magnetic field detector that's 1000 times more efficient than previous examples.
One way to measure magnetic fields is to shine laser light through synthetic diamonds with nitrogen vacancies — points where a carbon atom is missing from the diamond lattice. When laser light passes though such a vacancy, photons bump an electron in the space into a higher energy state; the presence of a magnetic field can affect the spin of that electron when its energy state drops back down, causing a difference in the new resting energy level. Measuring the differences in the energy states allows scientist to measure the strength of a magnetic field.
The only problem is that a lot of such readings are required to accurately measure a magnetic field. Usually, lasers have been shone at the surface of a synthetic diamond, limiting the number of readings that can be acquired. Now, the MIT team has developed a diamond chip in which laser light can bounce around inside — like a ball on pool table — providing a path length of over a meter and, in turn, yielding far more readings than in the past. The result is a sensor that's 1000 times more efficient than those that have gone before it.
The researchers reckon they could be able to create a miniaturised version of the chip that could be used in battery-powered devices — making accurate magnetic field measurement truly mobile. [Phys.Org]