Hidden Silicon-Vacancy Centers in Diamond

Color centers in diamond—in particular, negatively charged silicon-vacancy (SiV^-) centers—have generated excitement recently as potential hardware elements in quantum networks and devices. The attention is due in part to the protective influence of diamond’s wide bandgap and weak magnetic susceptibility, and in part to the technology available for manipulating and detecting light at these photon energies. In spite of this, open questions remain concerning the optical properties of SiV^- centers and related defects, and there exist significant opportunities for elucidating these properties using nonlinear optical spectroscopy. Here we report measurements on a high-density sample of negatively charged SiV^- centers in diamond through the use of collinear optical multidimensional coherent spectroscopy (MDCS). Using the technique, we have uncovered a hidden population of centers that not typically observed in photoluminescence, and which exhibit a high degree of spectral inhomogeneity and longer-than-expected single-particle electronic T₂ dephasing times. The phenomenon is likely caused by strain, indicating opportunities for controllably mediating electronic coherence in color-center-based quantum devices.