Mechanism of IR assisted charge state conversion of nitrogen vacancy centre in diamond

Abstract

The negatively charged state of nitrogen vacancy centre (NV^–) in diamond have been exploited in recent studies of magnetometry and quantum information processing. Nevertheless, the useful signal of NV^– for these applications can be deteriorated by the neutrally charged state (NV⁰) which acts as backgrounds. In recent studies, it has been reported that simultaneous excitation of green (532 nm) laser combined with infrared (1030, 1040, 1064 nm) laser can enhance the emission from NV^– while suppressing signal from NV⁰. Under such laser excitation conditions, however, the underlying mechanism of the photo-induced conversion between two charged states is still not fully understood. In our work, based on multi-photon absorption of IR, we propose a simple model to explain the mutual contribution of green and IR lasers to promote the NV^– population. Our model recovers the detailed featured observed in our experiment, and also can reconcile the results in previous literatures.