The Mechanism Of Hanle Absorption Spectrum In The Present Of Transverse Magnetic Field

Since the emergence of quantum coherence effects,such as CPT,EIT,and EIA,are often accompanied by the generation of sub-natural line widths,there are numerous appli-cations in many fields,for example,atomic clocks,atomic magnetometers,optical pulse manipulation,optical storage,and quantum teleportation.In recent years,The application of a transverse magnetic field BTMF the Hanle configuration has been studied extensive-ly.In these studies,BTMF is very significant.Among them,studies of the Hanle absorption spectrum have found that there is a split in the center of the absorption spectrum that is proportional to the intensity of BTMF This article focuses on the formation mechanism of this phenomenon.We consider a closed Fg =1?Fe = 0 transition of the 87Rb D2 line.The quanti-zation axis(z axis)is set along the direction of scanning magnetic field Bz which causes the Zeeman splitting of the ground.The quantization axis(z axis)is set along the direc-tion of propagation of the light beam,therefore light beam become the combination of ?+and ?_polarization.And in our system,the pump laser field is resonant with the atomic transition.The additional transverse magnetic field BTMF perpendicular to the propagation direction of the light beam,is used to redistribute the population and creat the coherence a-mong the ground state sub-levels.The Zeeman split is scanned by changing the magnitude of Bz,and then the Hanle absorption spectrum of the system can be derived by measuring the transmitted laser light.When the direction of the transverse magnetic field BTMF is adjusted to be perpendic-ular to the polarization direction of the laser,the dip at the center of the CPT absorption spectrum will be widened.Meanwhile,splitting occurs at the center of the spectrum,mak-ing the spectrum type a double-dip structure,and the interval between the two minimum points is proportional to the size of the BTMF Subsequently,we analytically solved the system and proved the proportional relationship between the splitting and BTMF We have clarified the physical mechanism in the dressed-state picture.That is,under the parameters corresponding to the position where the minimum value occurs,the distribution of the pop-ulation in the dark state reaches a maximum value.Therefore,the absorption is minimized here.The value thus forms two absorptive minima.Moreover,it can be clearly seen from the analytical solution that the collision interaction between the ground state sub-levels plays a key role in the occurrence of splitting.When changing the angle between BTMF and the polarization direction of the laser,the total spectrum will gradually change from a dip to a peak.This means that our system changes from a dark resonance to a bright resonance.At the same time,whether the angle is in the dark resonance or in the bright resonance region,there is always a symmetrical split in the spectrum.We give the analytical expression of the splitting width and study the physical mechanism of splitting evolution under the modified state.Moreover,we also point out the possibility of measuring the direction of the magnetic field by measuring the splitting width.