Fluorescence correlation and low temperature linewidth of single defect centers in diamond

Abstract

Low temperature fluorescence excitation spectroscopy was carried out on single nitrogen vacancy defect centers. At temperatures below 90 K the fluorescence intensity of individual centers drastically diminishes because of the population of a metastable singlet state in near resonance with the optically excited state. Low temperature fluorescence excitation spectroscopy down to 5 K becomes possible via deshelving of this state with a second laser source. Surprisingly individual centers reveal low temperature fluorescence excitation line widths around 0.6 meV.