| Microwave measurement technology plays an important role in radar detection,command communication,chip electromagnetic compatibility measurement and other fields.The existing microwave measurement instruments and equipment are usually bulky,high power consumption,complex and difficult to be portable,so it is urgent to carry out miniaturization research.The nitrogen vacancy color center in diamond has become one of the main research points of miniaturized quantum devices due to its excellent characteristics such as high sensitivity,high resolution,atomic size and compatibility with micro-nano fabrication.However,in the procession of miniaturization and engineering,due to the reduction of each functional component,the sensitive area is reduced,and the noise coupling between the functional components becomes larger,resulting in low microwave detection sensitivity,large system noise and poor anti-interference ability.Therefore,it is urgent to develop a new type of high spectral resolution,miniaturization,high sensitivity and portable diamond atom spin microwave measurement technology.Based on the above research background and current situation,we carried out research on microwave signal detection based on NV color center ensembles in this dissertation.The main research contents are as follows:1.A double resonant microwave frequency measurement method is proposed,frequency resolution is below 20 kHz,error of microwave frequency measurement within 100 Hz could be achieved combined with differential processing.An optical detection magnetic resonance system for microwave measurement was built based on the population distribution in ground state two-level system of the NV color center under the action of two route microwave and the physical model of the EIT-like two route resonance microwave measurement method.The microwave measurement system composed of diamond sample containing NV color center,pump laser,microwave and fluorescence collection equipment was described in detail.In information reading step,the magnetic resonance signal spectrum containing the microwave signal to be measured was obtained through fluorescence voltage acquisition and processing.The swept microwave signal with determined frequency,power and time was applied to the continuous microwave signal with unknown frequency,and the microwave frequency to be measured was obtained according to the shape and position of the resonance peak.The results of multiple measurement experiments show that the frequency of the microwave signal solved by this method is stable and repeatable,and is not affected by the phase synchronization of two microwaves.The resonance peak width is within 20 kHz,which could achieve the microwave frequency resolution within 20 kHz,and the frequency measurement is not affected by the change of scanning microwave power.By adjusting the magnetic field,the measurement range could be extended to more than 100 GHz.After the effect verification,the frequency measurement error could be controlled within 100 Hz by differential processing of the resonance peak.2.A microwave intensity enhancement device based on complementary split ring resonant structure is designed,the microwave intensity whose frequency within 2.74-2.8 GHz could be enhanced to 3.2 times.Local microwave intensity enhancement device is designed based on mechanism of microwave power measurement.Performance when microwave acting on complementary split ring resonator was analyzed,and structure parameter was optimized with electromagnetic simulation software.The microwave intensity enhancement ability of structure was characterized by the reconstructed optical detection magnetic resonance system,metal patch worked as electric dipole in structure was used to reflect fluorescence,fluorescence collection results was increased by 1.5,and sensitivity characterized by magnetic field measurement could be increased to 1.7 times,rabi results show that it has a uniform microwave intensity region of 250 × 75 μm2.In order to obtain the reference object,the ohmic microwave radiation structure is optimized,and Rabi frequency can reach 3.5 MHz,the corresponding microwave magnetic field intensity is 1.25 Gauss.Under the same microwave input power,the Rabi frequency of the complementary split ring resonator can reach 11.3 MHz,the corresponding microwave magnetic field intensity is 4.04 Gauss,indicating that the designed complementary gap ring structure could increase the local microwave intensity to nearly 3.2 times.3.Method of increasing the pumping power and dual-drive modulation and demodulation method is proposed,noise in optical detectable system is optimized,equivalent sensitivity of the magnetic noise spectrum is reduced to one-eighth of the original.Firstly,the influence of full width at half maximum and fluorescence intensity on microwave frequency measured through continuous wave electron paramagnetic resonance was analyzed,and the method of increasing laser pump power is proposed.In the experimental test,increasing the pump power to 6 times can narrow the full width at half maximum of the optical detection magnetic resonance peak by 12.5%.Then the effects of laser pump power and microwave power on the NV color center ensemble temperature were studied.Infrared camera measurement results show that the color center ensemble temperature drift could reach more than 80 K.In order to eliminate the temperature interference in detection and track the resonant frequency,a double-drive microwave frequency tracking method is proposed and experimentally tested,dual resonant frequency difference determined by the external magnetic field measured is within 25 kHz.The noise spectrum equivalent sensitivity is used to characterize the performance improvement,it is found that it can be increased from 10 nT/Hz1/2 to 1.2 nT/Hz1/2,which is reduced to one-eighth of the original.The above research passes experimental test.The proposed measurement method and designed device have good effect on microwave measurement method based on NV color center.It has good academic significance and engineering application value,could broaden the practical application range of NV color center microwave measurement method. |
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