Single-beam room-temperature atomic magnetometer with large bandwidth and dynamic range

We present a single-beam atomic magnetometer operating at room temperature for the measurement of ac magnetic fields. The magnetometer functions in the non-linear regime of magneto-optical rotation of $^{85}$Rb atomic vapour. We demonstrate a sensitivity of $\sim 0.9$ pT$/ \sqrt{Hz}$ at 2 kHz and a large bandwidth of 24 kHz. The dynamic range of measurement is $10^6$, making the sensor effective even in Earth's field. We present the signal-to-noise and bandwidth characteristics of the system for both shielded and unshielded modes of operation. Moreover, we perform theoretical analysis for the atom-light system for the single laser beam configuration. The effect of light intensity and detuning on the magnetometer are studied theoretically as well as experimentally to understand the strengths and limitations of the technique.