Bragg Diffraction Of Light Based On Electromagnetically Induced Grating In Rydberg Atom And Its Manipulation

In recent years,the study of ultracold Rydberg atoms has become an important re-search tendency in atom,molecule and photophysics.Compared with ordinary atoms,the outermost electrons of Rydberg atoms are in a highly excited state,so they have large atomic size,electric dipole moment,polarizability and longer lifetime.In addition,the dipole-dipole interaction between Rydberg atoms can be regulated in the range of 12 orders of magnitude,resulting in a lot of particular phenomena such as collective rabbi oscillation,Rydberg blockade and so on.Rydberg atoms have a wide range of poten-tial applications due to their physical properties,including the realization of quantum information and computation,multibody physical simulation,and the development of quantum nonlinear optics.The discovery of electromagnetically induced transparency(EIT)effect realizes the lossless propagation of incident light in the medium under the condition of reso-nance.Therefore,under the condition of very weak incident light intensity,optical media can also have significantly enhanced optical Kerr nonlinearity,which greatly promotes the development of weak light nonlinear optics and its applications in high-order harmonic generation,all-optical switching,and optical information processing and transmission.Because the EIT effect can effectively transform the long-range in-teraction between Rydberg atoms into non-local Kerr nonlinearity,the non-local Kerr nonlinearity in the Rydberg-EIT system is 4 to 5 orders of magnitude larger than that in the traditional EIT system.Non-Hermitian optical system is also an area of concern.When the refractive index of the optical medium is an even function of the space and the gain / loss is an odd function of the space,the incident light can propagate stably in the optical medium and is not affected by the gain / loss of the medium.In fact,the refractive index and gain/ loss of the medium correspond to the real and imaginary parts of the optical potential,respectively.If the optical potential of the medium satisfies the symmetry mentioned above,the optical medium satisfies the Parity-Time(PT)symmetry.Using the atomic system,especially the Rydberg atomic system,to realize the optical medium with PT symmetry not only has important scientific significance,but also has great application value.In this paper,the linear and nonlinear Bragg diffraction of light in PT symmetric electromagnetic induced grating(EIG)based on Rydberg atom is studied.In addition,the deflection and manipulation of spatial optical solitons caused by PT symmetric EIG are also studied.The main content of this paper includes the following three parts:1.The implementation scheme of PT symmetric EIG in Rydberg-EIT system is proposed.When dealing with the interaction between light and atoms,we first write the Hamiltonian of the system,and then derive the Bloch equation of the system and the Maxwell equation which describes the propagation of probe light.Then,the nonlinear response function of the system is obtained by using the transcendental mean field the-ory,and the first-order linear polarizability and the third-order nonlinear polarizability are obtained,in which the optical potential of the system is given by the first-order lin-ear polarizability.Finally,by introducing the spatial dependence of control light and auxiliary light,the optical potential satisfying PT symmetry is realized,and then the EIG satisfying PT symmetry is realized.2.The linear and nonlinear Bragg diffraction of light caused by PT symmet-ric EIG are studied.By using the Green function and writing the Bragg diffraction equation,we find that when the probe light on the incident PT symmetric EIG is weak,the EIG can produce a unique asymmetric diffraction pattern,and the asymmetry of the diffraction pattern is related to the EIG gain / loss coefficient,and reaches the peak when the PT symmetry of the EIG is broken.When the input power of the probe light is high,the Kerr nonlinearity and non-locality of the system can affect the morphology and asymmetry of the diffraction pattern.Because the system has a large Kerr nonlinear effect,the power of nonlinear Bragg diffraction pattern can be very weak.In addition,the gradient magnetic field can also be used to control the morphology and asymmetry of the Bragg diffraction pattern.3.The weak optical soliton deflection and its manipulation caused by PT symmetric EIG are studied.By using numerical simulation,we study the formation of optical solitons in the probe field before reaching EIG and the soliton deflection after EIG.Because the system has a large Kerr nonlinear effect,the generating power needed for the detection light to form optical solitons can be very weak.In addition,we can control the deflection degree and state of solitons by changing the gain / loss coefficient of EIG,the period of EIG,the Kerr nonlinearity and nonlocality of atoms,and realize the active manipulation of soliton propagation.The theoretical model,calculation method and research results proposed in this paper are of great theoretical significance for the study of Bragg diffraction of light in PT symmetric EIG based on Rydberg atom and soliton deflection and its manipula-tion caused by PT symmetric EIG.It has a certain guiding significance for exploring the potential applications of physical phenomena such as Bragg diffraction and spatial optical soliton deflection in precision measurement,optical information processing and transmission.