Nonlinear Magneto-optical Rotation (NMOR) Atomic Magnetometer Based On Rubidium

Atomic magnetometer is an sophisticated instrument for measuring weak magnetic field,which based on the Larmor precession of the polarized atomic spins.From the original compass indicating directions to the most sensitive Spin-exchange relaxation free(SERF)and superconducting quantum interference device(SQUID)magnetometer,people have never stopping devoting to developing the more sensitive,sophisticated,portable,low-power magnetometer.The study systematically introduces the nonlinear magneto-optical rotation(NMOR)magnetometer.The magnetometer based on the mechanism of NMOR is totally different from the SERF magnetometer.The achievements will be introduced below.Optical part: The whole light path has been redesigned.We detect the weak magnetic field by using a single linear polarization probe beam.The signal has a gain of two or three times after adding the circular polarization pump beam.Heating chamber and the supporting structure: The Heating chamber and the supporting structure have been redesigned.We put the Rb cell filled with 7Torr He inside the supporting structure.The heating wire can be easily wrapped on the surface of the cell which is easy-operating than the heating plate used before.Moreover,the supporting structure makes the internal light path more stable and convenient.Coil structure: We have first designed three pairs of Helmholtz coils ranging from-60300 nT to 57000 nT.The large scanning range help us quickly find the signal.In order to make NMOR magnetometer more sensitive,we also make some improvements to the coils inside the magnetic shielding.The scanning range has been doubled by using a set of coil with twenty turns.Measurement at room temperature: Now the sensitivity in the magnetic shielding tube is 0.02mrad/nT and it can reach 0.035rad/n T if measured at forty one degrees.Though there is a gap compared with the SERF magnetometer completed before,the NMOR magnetometer can measure weak magnetic field at room temperature and it's structure becomes easier.Besides,we use the glass cell filled with 7Torr helium,which can not narrow the line width effectively.In the future,we plan to choose a glass cell plated with paraffin instead and the sensitivity will be raised by over an order of magnitude.