All-optical magnetic recording with circularly polarized light

We experimentally demonstrate that the magnetization can be reversed in a reproducible manner by a single 40 femtosecond circularly polarized laser pulse, without any applied magnetic field. This optically induced ultrafast magnetization reversal previously believed impossible is the combined result of femtosecond laser heating of the magnetic system to just below the Curie point and circularly polarized light simultaneously acting as a magnetic field. The direction of this opto-magnetic switching is determined only by the helicity of light. This finding reveals an ultrafast and efficient pathway for writing magnetic bits at record-breaking speeds.     

Generation of an axial magnetic field from photon spin

In circularly polarized light the spins of the photons are aligned. When a short intense pulse of circularly polarized laser light is absorbed by a plasma, a torque is delivered initially to the electron species, resulting primarily in an opposing torque from an induced azimuthal electric field. This electric field, in general, has a curl and leads to the generation of an axial magnetic field. It also is the main means for transferring angular momentum to the ions. The time-dependent magnetic field has a magnitude proportional to the transverse gradient of the absorbed intensity but inversely proportional to the electron density, in contrast to earlier theories of the inverse Faraday effect.     

Relativity versus the longitudinal magnetic field of the photon

The longitudinal magnetic field ascribed by Evans to a circularly polarized electromagnetic wave is discussed. It is proved that this theory is inconsistent with special relativity.     

Circularly polarized X-rays probing nuclear magnetic moments and magnetism of solids

It is demonstrated how circularly polarized x-rays can be used in nuclear and solid state physics. Detection of the radiation pattern of circularly polarized x-rays emitted in highly converted decays of oriented radio isotopes allows the determination of nuclear magnetic moments. Studying the absorption profiles of energy-tunable intense circularly polarized x-rays emitted from high-energy electron storage rings provides a powerful method to determine spin structure of electronic states, local magnetic moments and magnetic short range order in ferromagnetic materials.     

Optical spin orientation of excitons in GaSe under longitudinal magnetic field

The degree of circular polarization of the free-exciton luminescence line has been measured in GaSe excited by circularly polarized light at 4.2 K under longitudinal magnetic field. The result shows that the spin relaxation time of exciton is field-dependent but the spin memory before reaching the exciton ground state is almost unaffected by the applied longitudinal magnetic field.     

Axial magnetic fields in relativistic self-focusing channels

Based on an improved cavitation model for the electron dynamics, an exact analysis is presented of the generation of axial magnetic fields in the relativistic self-focusing channels produced by circularly polarized light in plasmas. Two kinds of waveguiding structures are considered: single-channel waveguides and plasma filaments surrounded by a light field. It is found that due to large electron density gradients in the cavitation plasma, magnetic fields of megagauss values with opposite directions separated by a neutral sheet, where the magnetic field passes through zero, can be produced.     

Plasma waves in a stochastic magnetic field

Propagation of circularly polarized waves along a spatially uniform but temporally fluctuating magnetic field is considered. It is shown that the coherent waves are damped. The results are compared with those for Krook's relaxation model.     

Theory of coupled mode oscillation in a laser with axial magnetic field

The nonlinear laser theory without noise is applied to calculate amplitudes, frequencies and beat frequencies of two circularly polarized modes in a laser with axial magnetic field. The resonator is allowed to have different damping constants for waves polarized inx- andy-direction. For small beat frequencies frequency locking occurs, and the modes combine to a linearly or elliptically polarized mode. The plane of polarization rotates with increasing magnetic field up to ± π/4.     

Polarization of line radiation in the presence of external electric quadrupole and uniform magnetic fields

The polarization of emission lines formed in a medium immersed in external electric and magnetic fields is studied. The electric field is assumed to be quadrupolar in nature, while the magnetic field is uniform. We show that the quadrupole electric field produces line splitting which is characteristically different from the Zeeman effect. While the line components emitted along the quantization axis are circularly polarized in Zeeman effect, they are, in contrast, linearly polarized in the case of a pure quadrupole electric field. The emission perpendicular to the quantization axis produces three linearly polarized components in Zeeman effect, whereas only two linearly polarized components are observed in the case of quadrupole electric fields. Lack of azimuthal symmetry in the quadrupole electric field leads to polarized line components which appear quite differently for different azimuthal angles of the line of sight.     

Motion-induced magnetic resonance of Rb atoms in a periodic magnetostatic field

We demonstrate that transitions between Zeeman-split sublevels of Rb atoms are resonantly induced by the motion of the atoms (velocity: approximately 100 m/s) in a periodic magnetostatic field (period: 1 mm) when the Zeeman splitting corresponds to the frequency of the magnetic field experienced by the moving atoms. A circularly polarized laser beam polarizes Rb atoms with a velocity selected using the Doppler effect and detects their magnetic resonance in a thin cell, to which the periodic field is applied with the arrays of parallel current-carrying wires.     

An exact solution of the relativistic equation of motion of acharged particle driven by a circularly polarized electromagnetic waveand a constant magnetic field

An exact solution is found for the relativistic equation of motion of a charged particle driven by a circularly polarized electromagnetic wave and a constant magnetic field. The explicit expressions of particle position and velocity are obtained for certain initial conditions. The results are of interest to the interaction of the high-power laser with the magnetized plasma, electromagnetically pumped free-electron laser with a guide magnetic field, propagation of electromagnetic wave signals through a re-entry plasma sheath in the presence of a strong magnetic field, and magnetic confinement plasmas     

Light-induced interaction between graphene and magnetic film in a cavity

An interaction mechanism between graphene and magnetic film in cavity is presented in this work. The pseudospin in graphene can indirectly interact with the spins in magnetic film by the media of a circularly polarized photons under the conditions of high temperature and intense laser field. The interaction energy as well as the average values of pseudospin and spin components are calculated according to a generating functional approach. This interaction mechanism provides a scheme of detecting the pseudospin polarization effect.     

Bremsstrahlung model of polarized radiation from magnetic white dwarfs

Motivated by the desire to provide a model for the polarized radiation observed from some white dwarfs, we calculate the intensities of right and left circularly polarized bremsstrahlung radiation emitted by electrons in the atmospheres of magnetic white dwarfs.     

利用原子的塞曼光谱对半导体激光器进行稳频

中性原子的超精细能级在磁场中产生塞曼分裂 ,另外 ,左旋和右旋圆偏振光激发下原子的跃迁选择定则不同 ,因此 ,原子在超精细塞曼能级间的吸收谱峰相对无磁场条件下的吸收谱峰有一定的移动。利用这一点 ,验证了一种简单、灵活的方法对半导体激光器进行稳频 ,使激光器的线宽稳到小于 1MHz。通过对实验结果的分析 ,发现由左旋和右旋圆偏振光激发引起的原子吸收谱峰移动之和与饱和吸收峰半高宽相等时 ,稳频效果最好     

Masterequation and Fokker-Planck equation for coupled modes of a laser with axial magnetic field

The distribution function for two circularly polarized modes in a laser with axial magnetic field is calculated. If the resonator has different damping constants for waves polarized in different directions, we find a coupling between the modes. To describe this coupling it is necessary to couple both modes to the same heatbath. Starting from a masterequation describing the damping of the atoms and the light field, we may transform the masterequation to a Fokker-Planck equation by introducing a quasi distribution function. By eliminating the atomic variables adiabatically we find a Fokker-Planck equation for the light field variables only. The solution of the Fokker-Planck equation is given in the stationary case above threshold and in the non stationary case below threshold.     

Dynamics of a magnetic moment of finite dipolar lattices in the AC field

Dynamic regimes of a magnetic moment of 2 × 2, 3 × 3, and 4 × 4 square dipole lattices in the linearly and circularly polarized ac magnetic field and the perpendicular static field have been investigated. The possibility of regular and chaotic precession dynamics of the magnetic moment of the lattices has been demonstrated. A shift of the main magnetic resonance owing to the dipole–dipole interaction and additional resonances have been revealed. Quasiperiodic regimes and bistability states with a metastable chaotic attractor have been discovered.     

Quasistatic magnetic fields generated by a nonrelativistic intense laser pulse in uniform underdense plasma

Quasistatic magnetic fields generated by nonrelativistic intense linearly polarized (LP) and circularly polarized (CP) laser pulses in an initially uniform underdense plasma in the collision-dominated limit are investigated analytically. Using a selfconsistent analytical model, we perform a detailed derivation of quasistatic magnetic fields in the laser pulse envelope in the collision-dominated limit to obtain exact analytical expressions for magnetic fields and discuss the dependence of magnetic fields on laser and plasma parameters. Equations for quasistatic magnetic fields including both axial component B_z and the azimuthal one B_θ are derived simultaneously from such a selfconsistent model. The dependence of quasistatic magnetic field on incident laser intensity, transverse focused radius of laser pulse, electron density and electron temperature is discussed.     

金属中逆法拉第效应的经典理论

研究电子在圆偏振光驱动下的经典动力学问题以及金属中逆法拉第效应(IFE)的经典微观机制.得到电子在圆偏振光驱动下的一个解,表明其运动轨道是螺旋线.忽略电子与磁场的相互作用,电子作绕平行于其初速度的轴、横截面为椭圆的螺旋线运动,产生了一个平行于其初速度、方向由圆偏振光的手征性决定的磁矩.磁矩的统计结果与Hertel从电子气整体出发得到的结果一致.     

The radiation from a charge moving in a plane wave field and a magnetic field

The methods of classical electrodynamics are used to consider the problem of the radiation from an electron moving in the field of a monochromatic circularly polarized wave and a uniform magnetic field directed parallel to the direction of propagation of the wave. Expressions for the total radiation intensity and for the angular spectral distribution of the radiation are derived. Certain particular cases are studied.     

High-density all-optical magnetic recording using a high-NA lens illuminated by circularly polarized pulse lights

We propose a method for high-density all-optical magnetic recording. Our analyses, based on the vector diffraction theory, show that owing to the inverse Faraday effect, circularly polarized laser pulses focused by a high numerical aperture (NA) lens can induce a small magnetization domain. For an example, the FWHM of the effective magnetization domain is 0.4646λ when NA=0.85. The magnetization direction is basically perpendicular to the surface of the optic-magneto film within the effective magnetization domain and the switching direction of magnetization can be controlled by the helicity of the incident circularly polarized light. These characteristics are useful to next-generation high-density all-optical magnetic storage.