Diamond Materials

Diamond Materials for Quantum Application

23. September 2014: The DFG research group FOR 1493 “Diamond Materials and Quantum Applications” goes into its second funding period. FOR1493 is a national research consortium funded by the Deutsche Forsch-ungsgemeinschaft.

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ERC Advanced Grant


Photo-induced ionization dynamics of the NV defect in diamond

Photo-induced ionization dynamics of the nitrogen vacancy defect in diamond investigated by single-shot charge state detection

The properties of the negatively charged nitrogen vacancy (NV) defect are usually exploited in various applications like magnetic field sensing and quantum information processing. However, the NV center in diamond can also occur in the neutral charge state (NV0). It has been shown that upon illumination (532 nm) a continuous ionization and recombination process of the NV defect is going on. This charge state dynamics was examined in detail in the present work utilizing different methods. Emphasis was on the excitation wavelength dependence.
In this study it was experimentally proven that a recently observed “dark” state of the negatively charged NV defect is indeed its neutral charge state. The rates of the ionization and recombination processes were measured for a broad range of excitation wavelengths. It was determined which wavelengths are optimum to gain maximum NV minus population. Additionally, the transition from a two-photon ionization process to a one-photon ionization process was observed by varying the excitation laser light from the green to the blue spectral range. This change in the ionization process revealed the energy level of the ground state of NV minus within the bandgap of diamond.
The work gives new insight into the photophysics of the NV defect. The detailed study of the charge state switching behavior allows for implementation of methods like Photoactivation Localization Microscopy (PALM) or Stochastic Optical Reconstruction Microscopy (STORM) with NV centers. This enables the resolution of single NV centers with distances well below the diffraction limit.

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