Figure 2
Demonstration of high dynamic range, bandwidth and sensitivity to magnetic field. (a) The raw unfiltered magnetic signal for a full 60 s iteration and (b) a zoomed 0.1 s segment of the same iteration. The signal was dominated by low frequency and DC laser power drift (\(<5\) Hz), 50 Hz and 150 Hz noise from mains electricity and higher frequency (\(>10\) kHz) noise and ranges between \(\pm 1\,\upmu \hbox {T}\), well within the dynamic range of the magnetometer. (c) Spectral density in pT/\(\sqrt{\text {Hz}}\) for a single 60 s iteration and (d) a spectrogram of repeated 60 s acquisitions over 10 h. The sensitivity floor is approximately 50 pT/\(\sqrt{\text {Hz}}\) with f(\(-\,3\,\text {dB})=4.8\) Hz defined by the lock-in amplifier low pass filter. Also indicated are calculations of the total noise, which includes electronic and shot noise, and of the estimated shot noise level alone. Many sources of background magnetic noise can be seen to peak well above this floor.
