Fiber Optic Diamond NV Color Center Microwave Magnetic Field Measurement System Based On FPGA

With the rapid development of microwave technique and the increasing demand of low power consumption and miniaturization of equipment,the size of microwave devices such as antenna and chip is decreasing and the integration degree is greatly improved.Thus,it brings new challenges and opportunities to the characterization of microwave magnetic field on the surface of the device and the electromagnetic compatibility test and failure analysis of the chip.The traditional microwave magnetic field detection method based on open metal waveguide can not meet the requirements of high spatial resolution and non-destructive detection.Therefore,this paper will study the microwave magnetic field measurement method based on diamond nitrogen vacancy color center in the quantum precision measurement system.As an inherent lattice defect in diamond,the nitrogen vacancy color center has stable optical properties and longer electron spin coherence time.It can realize the manipulation and reading of spin quantum state at room temperature.Therefore,it is widely used in quantum measurement field.In this paper,a fiber optic diamond nitrogen vacancy(NV)color center microwave magnetic field measurement system based on field programmable gate array(FPGA)is proposed.The experimental system can achieve high spatial resolution and non-destructive measurement of micro wave magnetic field on small antenna and chip surface.This paper innovatively designs a tapered fiber-optic diamond NV color center microwave magnetic field probe.The probe fixes the submicron diamond sample at the end of the tapered fiber,which can be very close to the surface of the device to be measured.Because it is a non-metallic structure,it will not cause interference to the microwave magnetic field to be measured.The spatial resolution of the magnetic field detection is related to the size of the diamond sample,It can reach submicron or even nanometer level.At the same time,in order to further improve the integration of the whole system,this paper also develops an integrated control and readout device based on FPGA technique,which is used to generate pulse control sequence.The collected weak fluorescent signal is processed by analog-to-digital conversion,filtering and finally by fast Fourier transform(FFT)realizes the function of spectrum analysis.In this paper,the microwave magnetic field imaging experiment of split ring resonator(SRR)antenna is carried out by using the measurement system,and the experimental results are basically consistent with the HFSS simulation results,which proves the feasibility and accuracy of the system.At the same time,the high spatial resolution of magnetic field detection of the system is proved by comparing with the results measured by traditional probes.The distribution information of microwave magnetic field in the same area of microstrip antenna is also characterized under the action of resonant microwave with different frequencies.According to the experimental results,the possibility of vector field measurement is proposed.By scanning the low-pass filter chip of Ga As monolithic microwave integrated circuit(MMIC),the detection ability of the system for the surface microwave magnetic field of MMIC chip is verified.