Cesium Atomic Magnetometer Based On The Cavity-enhanced Magneto-optic Polarization Rotation

Magnetic field measurement has important research significance in materials testing,biomedicine,mineral exploration,military development and other fields.With the continuous expansion of the application field of magnetometers,miniaturization and integration are the development trends of magnetometers.The rotation angle and the signal-to-noise ratio are key factors for the sensitivity.Under the condition that the various parameters are constant,the multi-reflective cavity can increase the optical power of the pump light and increase the effective length of the interaction between light and alkali atoms as the magnetic-sensitive medium.It is an efficient way to improve the magnetic-measurement sensitivity.There are many types of multi-reflective cavities,the resonant cavity can keep the light beam in the process of multiple reflections between the two cavity mirrors without causing DC noise due to factors such as astigmatism and refraction,and thus becomes a better choice for improving the magnetic measurement sensitivity of a magnetometer.This thesis focuses on the relationship between the cavity enhancement factor of the sensitivity to magnetic field and the cavity mirrors’ reflection under the condition that the atomic gas cell has a certain loss of light intensity.The following specific work has been completed:1)The history of the magnetic field measurement is introduced,the current situation of the multi-reflecting cavity-enhanced magnetometer system and comparation of advantages and disadvantages between different types of reflecting cavities are presented.2)Theoretical calculations shows that the cavity enhancement factor is simultaneously affected by the reflectivity of the cavity mirror and the cavity escape efficiency.The mirrors’ reflectivity and cavity structure suitable for this experimental plan are designed and selected.3)The magnetometer with compact structure and simple system adopts a plano-concave standing wave cavity,the reflectivity of its input and output coupling mirror is 99.5% and 88%,respectively.When the light loss in the atomic vapor is 9.5% and 8.5%,the corresponding cavity escape efficiency is 38.1% and 40.7%,and the sensitivity to the magnetic field is decreased with the cavity by 4.41 and 5.01 times,respectively.Under the condition of ensuring the strength of the interaction between light and atoms,as the loss of light intensity by the atomic gas cell is reduced,cavity enhanced effect is more pronounced and the sensitivity is further improved This article provides a certain theoretical reference and effective scheme for the selection of cavity mirrors in the subsequent experiments using cavities to increase the strength of the interaction between light and atoms.