A full optically operated magnetometer array: An experimental study

Abstract

We show the operation of an optically pumped magnetometer array in a 50 μT magnetic field. The various components for a fully optical and non-magnetic detector unit were constructed and evaluated, from which a prototype unit was assembled with fiber coupled electronics. In this unit the magnetometers were operated using the intensity modulated method and heated with an off-resonant laser. Calculations on the temperature distribution were used to design the magnetometer array. Different magnetometers in such a detector unit were characterized and showed identical performance. Without applying noise reduction schemes, the obtained magnetic field resolution is a factor 2.5 above the shot noise level down to frequencies of about 7 Hz.

Suppression of spin-exchange relaxation in tilted magnetic fields within the geophysical range

“…• C) due to the large heat capacity of the silicon parts [34], the absolute measurement of the temperature of the alkali vapor is difficult. At high temperatures, when the relaxation is dominated by spin-exchange collisions, an uncertainty in temperature of ±1…”

“…The ambient static magnetic field is controlled in magnitude and direction by a triaxial Helmholtz-coil system that is placed inside a threefold cylindrical μ-metal magnetic shield [19]. The cell temperature is set by exposing the lateral silicon parts of the cell array to fiber-coupled heating laser radiation (λ = 808 nm) [34] and gets monitored by a nonmagnetic fiber-optical sensor thermally connected to the cell's bulk silicon.…”

An Optically Pumped Magnetometer Working in the Light-Shift Dispersed Mz Mode

“…For that reason, for a long time the use of large vapor cells was the silver bullet for high resolution [19,22]. Recently, also the opposite has been tried, because smaller alkali vapor cell volumes offer the possibility of integration with other functional parts of the complete magnetometer (like pump laser diodes and photo detectors [23]) or the combination of various cells with identical properties [24], which can be used for signal improvement [25,26]. Moreover, small cells are a good choice for measurements, where an adequate lateral resolution is requested, like in biomagnetism [27].…”

Chip-scale atomic devices

“…124 Processes have also been developed to separate and thermally isolate cells, while maintaining the rigidity of the array spacing by using a common window for all cells in the array. 139 Finally, multiple cells can be connected by channels to the same reservoir to form arrays of cells with the same buffer-gas pressure, 153 as shown in Fig. 19.…”

“…Magnetometer arrays based on this multi-cell approach have also been demonstrated for magnetic gradiometry and imaging. 153 Glass cells with thicknesses between 20 lm and 200 lm have also been fabricated using lithographic glass etching techniques. 154 …”