Broadband Laser Amplification Of Diamond NV Center And Its Magnetic Sensing Properties

As the hardest material in the world,diamond has always been the focus of scientific research.In particular,the nitrogen-vacancy(NV)center in diamond shows bright and stable fluorescence in visible range,making it possible for people to develop NV-based tunable laser.Besides,because the spin of NV center is controllable under ambient condition,it also plays a vital role in quantum sensing,especially magnetic field sensing.In this paper,the research of NV center in laser amplification and quantum magnetic sensing is investigated and studied,where broadband laser amplification and magnetic resonance measurement under high-power excitation are both achieved.Firstly,the laser amplification of NV center was observed at four wavelengths(636.2 nm,656.1 nm,684.4 nm and 726.6 nm)in its fluorescence range by NV-based laser amplification technology,obtaining the relationship between the parameters of pump light and seed light and the amplification effect.The excitation conditions were further optimized,where the polarization angles of both pump light and seed light were set to 0°,and the seed power was low whereas pump power was high,then the best amplification was achieved at a wavelength of 726.6 nm,with an amplification factor of 1.56,which is helpful for the realization of broadband laser amplification based on NV center.Secondly,with the help of optical detected magnetic resonance(ODMR)measurement technology,highly sensitive and fast magnetic field measurement was demonstrated on ensemble NV center under high power excitation,where both contrast and signal-to-noise ratio(SNR)are improved,and the circle of frequency scan is reduced to 1,resulting in greatly shortening of the time for magnetic field detection.Based on optimal excitation conditions,a spatial magnetic field was then applied,and the components,including the intensity(B₁,B₂,B₃)and polarizing angle(?₁,?₂,?₃),of the magnetic field in three orientation directions of NV centers(ê_NV1,ê_NV2,ê_NV3)are deduced from the ODMR spectral lines,providing a solution for high-speed reconstruction of magnetic field vectors using NV centers.Lastly,combining NV-based laser amplification and quantum magnetic detection technology,the laser amplification signal of NV center replaced its fluorescence signal as readout signal for magnetic field sensing,so that the collection efficiency and beam quality of the readout signal were both improved.After the optimization of laser amplification,it was observed that the intensity of readout signal decreased by 1%due to the magnetic field at the seed light wavelength of 726.6 nm,which plays a certain role in promoting the remote magnetic field sensing of NV center.