Imaging And Light Field Measurement Based On The NV Center In Diamond

Quantum sensing as an emerging field has received a lot of attention in recent years.Quantum sensing techniques use special substances(such as superconductors,quantum dots and solid state defects)as probes that allow high precision measurements of physical quantities.Characterization of these probes with high spatial resolution in the nanoscale range can lead to significant performance improvements of the related quantum sensing techniques.Diamond NV centers are one of the most common solid-state defects that have been widely used in quantum sensing.NV centers are chemically inert,with bright and stable fluorescence,long coherence time,and their own size is only at the atomic size level.These advantages allow NV centers as an ideal probe to play an important role in high-resolution imaging,temperature sensing,electromagnetic field vector distribution measurements,etc.For example,by introducing NV centers into cells as fluorescent markers,optical imaging of biological tissues or organs can be achieved.Meanwhile,changes in the internal environment of cells can be monitored by using the spin properties of NV centers.The high-resolution optical characterization of NV color centers is important in these applications.Unfortunately,conventional optical imaging systems are constrained by the diffraction limit and cannot measure NV centers with high spatial resolution.The existing super-resolution imaging techniques for NV center characterization experiments have disadvantages such as low imaging contrast,high laser power used,and complex imaging systems.In order to improve the above-mentioned shortcomings,this thesis investigates the charge state property of NV centers,uses this property for optical super-resolution imaging of NV centers,and uses NV centers for high-precision characterization of vector light fields.The main achievements in this thesis are shown below:1.The charge state transition conversion of NV centers in nanodiamonds was studied.The process was analyzed theoretically,and an experimental system was established to measure the charge state conversion process of NV centers in nanodiamonds with different sizes.The measurement results prove that the charge state conversion process of the NV center is a two-photon process and is affected by the surface environment.2.Charge state depletion nanoscopy was proposed based on the charge-state conversion process of NV centers in nanodiamonds.The principle of charge-state depletion nanoscopy is discussed and a charge-state depletion imaging system containing a chopper and can integrated with a commercial microscope was built.The system has the advantages of low cost,high laser utilization,and integration with other imaging systems,further is more suitable for biological imaging.The system was used to optically image a single 50 nm diameter nanodiamond NV center and finally obtained a lateral resolution of 77 nm.At the same resolution,the depletion laser power applied in charge state depletion nanoscopy was only 6.3%of the depletion laser power applied in stimulated emission depletion imaging technology.Further,a procedure for introducing nanodiamonds into cells was presented,and charge depletion nanoscopy was successfully implemented in living organisms.3.A high-precision vector light field characterization method was proposed.Using individual NV centers with different spatial axial distributions in the block diamond to interact with the unknown light field,the vector light field distribution under tightly focused conditions can be reconstructed with nanoscale resolution with the help of a prior knowledge and deep neural networks.This method has the advantages of stable measurement process,no probe perturbation,and predictable results.This technology not only helps to improve the performance of charge-state depletion nanoscopy,but also further extends the application of NV center sensing systems.In conclusion,this thesis utilizes diamond NV centers for high precision sensing measurements.High spatial resolution optical imaging was achieved using the charge state properties of NV centers in nanodiamonds;high precision measurement of the light field vector distribution under tight focus condition was achieved using NV centers with different axes in the bulk diamond.These works have important significance for further applications of NV centers in the field of quantum sensing.