Light-narrowed optically pumpedMxmagnetometer with a miniaturized Cs cell

Abstract

We demonstrate a way of operating an optically pumped magnetometer with miniaturized cesium cell using the light-narrowing effect. The magnetometer setup shows improvement of shot-noise-limited sensitivity (42 fT/ √ Hz in a cell of only 9.3 mm 3 volume) due to the suppression of spin-exchange relaxation to a large extent and the use of a strikingly increased fraction of alkali-metal atoms for signal generation, working even in μT magnetic fields, by using only a single high-intensity laser beam both for pumping and probing of atomic spins.

Alkali-vapor magnetic resonance driven by fictitious radiofrequency fields

“…The pump polarizes the F = 4 manifold by depopulating the F = 3 manifold, while producing minimal light shift and broadening of the F = 4 magnetic resonance [31]. Moreover, we can see narrowing (∼ 10%) of the spin-exchangelimited resonance line [32,33] due to the high polarization in the vapor.…”

Chip-scale atomic devices

“…209 Light narrowing was demonstrated in a magnetometer based on a microfabricated Rb vapor cell. 211 Considerably more laser power was required to achieve the high atomic polarization needed for light narrowing but the sensitivity was improved from 1.5 pT/ͱHz without light narrowing to 42 fT/ͱHz. This sensitivity was achieved at a field of 5 lT showing that femtotesla sensitivity can be achieved in a microfabricated vapor cell in a high-field environment.…”

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

“…The effect of higher buffer gas pressure was one of the features in the subsequent operational mode, called “Light-Narrowing (LN)” [34]. As can be seen in Figure 2, the higher the buffer gas pressure, the more the four absorption lines are broadened and overlapped.…”

“…This can be seen in Figure 3a,b which show the population of the Zeeman levels in both ground-states levels for the normal and the LN M x mode. In consequence, all atoms contribute to the measurement signal, what increases the steepness $\left|\mathrm{normald}{I}_d/\mathrm{normald}{f}_{B1}\right|$ of the dispersive lock-in signal by two orders of magnitude [34]. The same effect can be achieved by substituting the single detuned laser by separate pumping on F = 4 and repumping on F = 3 [31,35], a common scheme in cold atom experiments [36].…”

“…In this case, using the off-resonant pumping technique described above, nearly all atoms can be pumped into the stretched state, the Zeeman state with the highest quantum number (Figure 3c). This enhances the signal further and also decreases spin exchange relaxation due to the light-narrowing phenomenon [34,38]. However, according to Bloom [18] the measured variable in the M z mode is just a secular change of the pumping light absorption, when the B 1 -field works at the Larmor frequency.…”