Photophysics of Quantum Emitters in Diamond and Hexagonal Boron Nitride
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2019-01-01 |
| Authors | Mads Boll |
| Institutions | Technical University of Denmark |
Abstract
Section titled āAbstractāThis thesis decay rate enhancement and photophysics of nitrogen vacancy (NV) centers in diamond and quantum emitters in hexagonal boron nitride (hBN). The NV center in diamond is a unique physical system that ļ¬nds use in many quantum technologies such as quantum sensing, quantum information processing and single photon generation. Consisting of a substitutional nitrogen atom next to a vacant lattice site, the NV center introduces discrete electronic energy levels within the wide bandgap of diamond. The NV center can be optically excited and will emit single photons upon relaxation that hold information of the spin state of the NV center. In this thesis, we use metallic structures to modify and enhance the decay rate of NV centers in bulk and nano diamonds in three diļ¬erent experiments. Such an enhancement is a way to improve the usability of NV as a single photon source. Using TiN ļ¬lms with metamaterial properties we observe a 2-fold decrease of the total excited state lifetime of NV centers in nano diamonds, when comparing to similar NV centers not inļ¬uenced by the TiN ļ¬lms. For shallow implanted NV centers in bulk diamond we experimentally investigate how a decay rate enhancement inļ¬uences the signal-to-noise ratio (SNR) in spin readout measurements. In this experiment we perform spin state readout before and after introducing a rate enhancement and ļ¬nd a 30 % drop in spin contrast. We model the spin readout measurements using a ļ¬ve-level model and use that to predict the SNR under higher rate enhancement. In the last NV related experiment we use a curved metallic mirror on top of shallow implanted NV centers, to measure the continuous lifetime modiļ¬cation as a function of distances to the mirror. This allows us to determine the internal quantum eļ¬ciency (IQE) by ļ¬tting the experimental data with a model that includes calculating the expected Purcell factor. We ļ¬nd IQE values of 0.70Ā±0.07 and 0.82Ā±0.08 for implantation depths of 4.5Ā±1 and 8Ā±2 nm, respectively. Last but not least, newly discovered bright single photon emitters in two dimensional hBN were investigated. Similar to the NV center they are believed to be crystal defects, but the defect conļ¬guration is not fully known. In this thesis, the photophysics of quantum emitters in hBN nano ļ¬akes are investigated. Intensity autocorrelation measurements indicate the presence of at least two metastable states, seen by distinct photon bunching levels on long time scales in the g(2)(Ļ)-functions. We also observe blinking behaviour, which we show can be explained by changes in the IQE. From rate equation ļ¬tting we ļ¬nd that transition rates scale linearly with excitation power. Based on the transition rates we estimate the IQE to be close to unity for excitation powers below saturation.
Tech Support
Section titled āTech SupportāOriginal Source
Section titled āOriginal Sourceā- DOI: None