Fast photophysical processes of a single NV center modulated by the near-infrared laser pulse

The photophysics of the nitrogen-vacancy (NV) center in diamond has been extensively investigated. Especially the fast optical switch based on the NV centers' photoluminescence (PL) by the near-infrared laser (NIR) modulation has been demonstrated, but the photophysical processes behind it are still not fully understood. Here, the NIR modulation on the PL of an isolated single NV center in bulk diamond is probed and detected with precision at picosecond timescale. We thereby observe NIR optical excitation at the NV ground state as well as at the excited state. Meanwhile, a generalized model is constructed with additional energy levels that can be reached under NIR illumination. The transition rates from numerical simulations are demonstrated in good agreement with the experimental results. Our findings may provide insights into the understanding of the NV center's related photophysics and open intriguing prospects such as reversible optical switching, super-resolution microscopy, and so forth.