Quantum emitters for sensing and sub-diffraction imaging
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A quantum system with discrete, resolvable energy levels is an ideal system for sensing applications, taking into account that it can strongly interact with its environment. Although the strong response with the target properties such as magnetic or electric field is ideal, it can be a disadvantage when the system is interacting with other physical changes (noise) at the same time. However, the benefits of the strong coupling as well as small size of the sensor has motivated many researchers to explore quantum systems for measuring very small physical quantities. For instance, Nitrogen vacancy center in diamond is a unique quantum system enabling sensing of magnetic field from single molecules or electrons at room temperature. This thesis has focused on two different quantum emitters: NV centers in nanodiamonds and quantum emitters in hexagonal Boron Nitride (hBN). In the first part a new assembly technique based on electron beam induced deposition and crosslinking chemistry is developed. It is demonstrated that fluorescent nanodiamonds containing NV centers can be assembled into arrays of various size and shapes on any substrate. The produced array is ideal for device fabrication due to its outstanding robustness. A potential application of such arrays as magnetic field sensor with high spatial resolution is shown. The superior properties of quantum emitters in hBN has been studied in the second part of this thesis, where is has been shown that these emitters are not only stable but also maintain their single photon purity at elevated temperature. The highest measured quantum emission at 800 K in this study is the highest reported temperature for a quantum emitter so far, makes them a suitable candidate for temperature sensing. In addition, the level structure of emitters in hBN has been investigated in detail which reveals the unique photophysical properties of a class of these emitters which result in a nonlinear increase in the emission upon co-excitation with two lasers of different wavelength. Finally the photophysic property of these emitters has been employed to introduce a new modality of super-resolution microscopy with resolution down to about 70 nm. These findings will extend our understanding of quantum emitters in hBN and introduce a new functionality for them which paves the way toward their application in biology and sensing.
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