Quantum diamond microscopy with optimized magnetic field sensitivity and sub-ms temporal resolution

Quantum diamond magnetometers using lock-in detection have successfully detected weak bio-magnetic fields from neurons, a live mammalian muscle, and a live mouse heart. This opens up the possibility of quantum diamond magnetometers visualizing microscopic distributions of the bio-magnetic fields. Here, we demonstrate a lock-in-based wide-field quantum diamond microscopy, achieving a mean volume-normalized per pixel sensitivity of 43.9 $\mathrm{nT\mu m^{1.5}/Hz^{0.5}}$. We optimize the sensitivity by implementing a double resonance with hyperfine driving and magnetic field alignment along the $<$001$>$ orientation of the diamond. Additionally, we show that sub-ms temporal resolution ($\sim$ 0.4 ms) can be achieved while keeping the per-pixel sensitivity at a few tens of nanotesla per second using quantum diamond microscopy. This lock-in-based diamond quantum microscopy could be a step forward in mapping functional activity in neuronal networks in micrometer spatial resolution.