Study On Physical Scheme Of Alkali Atomic Magnetometer Based On Faraday Rotation

The miniaturized,low-power,high-sensitivity atomic magnetometer has great value of application in the fields of biomagnetism,geomagnetism,and military anti-submarine.Therefore,designing a compact atomic magnetometer with a simple structure is one of the development directions of magnetometer.The work in this thesis is based on the phenomena of electron paramagnetic resonance and synchronous optical pumping technology,and is committed to provides feasible method for miniaturized and even chip-scale magnetometers.The main contents of this thesis are as follows:(1)The theories of atomic magnetometers are introduced and analyzed.This thesis use optical Bloch equation to deduce and model the evolution state of the magnetic moment,the physical mechanism of magnetic resonance is explained by using the time-dependent perturbation theory of quantum mechanics.The physical principle of Faraday rotation is explained,and the measurement method of Faraday rotation commonly used in magnetometer experiments is introduced.The physical and optical properties of 87Rb atom are also introduced,which provides theoretical support for the experiment of the atomic magnetometer.(2)An all-optical atomic magnetometer scheme using a single beam is designed and realized.We periodically modulate the light synchronously with Larmor precession frequency,so that the laser converts periodically between polychromatic and monochromatic.When the light is polychromatic,the ±1st sidebands of the light are optically resonant with the atoms,and the atoms are polarized by pumping.When the light is monochromatic,a differential detection technique extracts the Faraday-rotation signal of the light,and the polarization of the light is probed.This scheme is suitable for miniaturized magnetic gradiometer and magnetic field probe array.(3)A single-beam magnetometer scheme based on the absolute measurement of Larmor frequency is designed and realized.We designed a polarization field along the direction of light propagation.The polarization field interact with the atoms synchronously with the pumping light to polarize the atoms.After each pumping cycle,linearly polarized light will record the information of magnetic moment.This scheme can be used to study the relaxation processes of the atomic,and also provides a method for absolute measurement of the magnetic field using a single beam.(4)A magnetometer scheme based on a single polychromatic laser beam is designed and realized.The scheme use the microwave to modulate the light from monochromatic to polychromatic,then the optical polarization converter is used to transform the polarization of each frequency sideband of polychromatic light.The circularly polarized carrier component of polychromatic light is used to pump the atoms,and the Faraday rotation angle of two orthogonal linearly polarized ±1st sidebands after passing through the polarized atoms is opposite.The linear polarization signal with atomic macroscopic polarization information is extracted by differential detection.The experimental results reveal that our scheme is suitable for miniaturized atomic magnetometer,or chip-scale magnetometer with a self-contained light source.