Transient spectroscopy of color centers in semiconductors and their application

This thesis investigates color centers in wide-bandgap semiconductors, which are crucial for quantum technologies. A transient absorption (TA) spectroscopy setup, spanning 400-2300 nm with nanosecond resolution, was developed for the investigation of their intricate electronic structures and dynamics over pump-probe delays reaching milliseconds and even seconds.

The present study focused on the investigation of nitrogen-vacancy (NV) centers in diamond and silicon vacancy (V_Si) centers in 4H-SiC. For NV centers, numerous previously unknown electronic states were discovered in both negatively and neutrally charged states (NV^- and NV⁰, respectively), and their inter-charge conversion was documented. This also included the first direct observation of tunneling-mediated charge conversion.

A magnetometer operating at room temperature, employing the NV-singlet absorption, has been demonstrated. This magnetometer demonstrated a noteworthy achievement, achieving a sensitivity of 18pT/√Hz, thereby eliminating the requirement for optical cavities. Subsequently, the photoexcitation dynamics of V_Si centers were reported, and the initial transition energies between their spin-doublet electronic states were identified. These findings significantly advance our understanding of color centers, with direct implications for quantum sensors, providing a foundation for future research in wide-bandgap materials.