Modeling fluorescence of single nitrogen-vacancy defect centers in diamond

Based on new spectroscopic information retrieved by experiments on individual Nitrogen-Vacancy (NV) defect centers in diamond, we introduced the five-level photophysical model of the center and demonstrate its applicability to describe consistently different experiments on single NV centers. The model takes into account the triplet-triplet character of the optical transition (3)A-E-3 (637nm) of the center and the presence of a metastable singlet state (1)A. Supposing optical excitation rates B-T from spin substates T = X, Y, Z of the ground (3)A state as well as the fluorescence emission rates A(T) to these substates to be different (B-Z/B-X approximate to 11, B-X = B-Y while A(Z)/A(X) approximate to 18, A (X) = A(Y)), we were able to fit consistently the experimental data obtained for green-laser-excited single NV centers at room-temperature: (i) lineshapes of fluorescence-detected magnetic resonance at 2.88 GHz in the ground (3)A state and their changes due to the strains in the diamond crystal, (ii) fluorescence saturation and (iii) photon antibunching/bunching in the fluorescence light emitted by a single NV center. (C) 2001 Elsevier Science B.V. All rights reserved.