Exploring solid-state defects with a microwave-modulated spectroscopy technique*

We have developed a microwave-based spectroscopy technique to determine charge state of nitrogen-vacancy ensembles in diamond. The technique isolates, in situ, the spectral shape of the fluorescence contribution from neutral and negatively-charged defects, producing sample-specific results which take into account the effects of experimental conditions (eg. illumination intensity and wavelength) and material properties (such as local strain and electric fields). Here, we use this technique to explore how ensemble charge state is affected by experimental and material parameters, and to study the physics of NV ionization from the negative charge state.
We also apply a variation of our technique to silicon vacancies (SiV) in 4H silicon carbide. The technique may be used to isolate the spectra of V1 and V2-type defects at room temperature -- these are two silicon vacancies that occur at in-equivalent lattice sites but have closely-spaced spectral signatures. We explore the modulation of the SiV signals in both bulk SiC and in nanobeam optical resonators that include the vacancies.