Research On Nanodiamonds Nitrogen-vacancy Center Sensing Characteristics And Fiber Integration Technology

In recent years,with the advancement of physics research,precision measurement technology represented by diamond nitrogen-vacancy(NV)center has developed rapidly.Owing to its good stability,long coherence time,laser manipulation and easy integration,the sensing methods based on NV center have attracted more and more attention.It has a good application prospect in the field of magnetic field,temperature,electric field and angular velocity sensing.With the application of NV center measurement technology,sensor systems with advantages of high integration,miniaturization and device formation become the development trend of NV measurement technology in the future.In this thesis,the integrated coupling technology of NV centers in nanodiamonds to optical fiber is studied.The content mainly includes nanodiamonds and fiber coupling way,fluorescence excitation and collection,geometrical optics simulation validation,the probe structure optimization and performance improvement.All-optical measurements of temperature,magnetic field and humidity were also carried out to further verify the coupling and integration performance of the probe.The main research achievements in this thesis are as follows:(1)An all-optical temperature sensing probe based on multi-mode fiber end face coupling nanodiamonds NV center were proposed and developed.The probe achieves efficient excitation and coupling of fluorescence signal based on UV adhesive nanodiamonds structure attached to optical fiber end face.Owing to the thermal expansion effect of UV adhesive,the probe has high temperature sensitivity and can accurately measure the ambient temperature.Compared with optical detected magnetic resonance(ODMR),all-optical measurement has the advantages of simpler,faster and lower cost.Compared with the previous fiber coupling method,the coupling method of fiber end hemispherical film has the advantages of simpler fabrication,better integration and higher fluorescence collection efficiency.(2)In order to further simplify the optical path and improve the collection efficiency of NV centers fluorescence,a coupling method of nanodiamonds and dual-fiber structure was proposed.Compared with the single-fiber hemispherical film coupling method,the fluorescence collection ability of the developed dual-fiber probe is improved by ～30.7%.The optical elements in the optical path are reduced,which improves the system integration.An all-optical measurement of environmental humidity was preformed by combining calcium alginate hydrogel film containing nanodiamonds with dual-fiber probe.The experimental results show that the dual-fiber coupling probe structure has a good response to the change of humidity.The probe also has self-calibration function based on the characteristics of NV centers fluorescence spectrum,which solves the problem of temperature cross talk of the probe.The study expands the application range of NV centers sensor probe.(3)Based on the method of light-induced self-written waveguide,a coupling method of growing waveguide cones containing nanodiamonds on the end face of optical fiber is proposed.This coupling method can further reduce the probe volume and realize physical quantity measurement in tiny space.By controlling the curing parameters of the self-written conical waveguide,the shape of the conical probe can be controlled effectively and the collection efficiency of the fluorescence signal can be changed accordingly.The existence of waveguide cavity can also induce the fluorescence resonance,and the resonant peak with narrow line width can be obviously generated at the specific wavelength position in the spectrum.Finally,the all-optical temperature and magnetic field measurement is carried out,and the temperature and magnetic field information of the external environment can be accurately obtained by comparing the intensity changes of the resonant peak.