Study On The Magnetic Field Characteristics Of A Focused Angular Angular Vortex

In the past decade, the interaction between optical field and magnetic-optical materials has potential in all-optical magnetic recording, atomic trapping, confocal and magnetic resonance microscopy, etc. By using the inverse Faraday effect induced by light, the focused vector optical field can produce a novel magnetic field distribution, which has become a hot research topic. Polarization is one of the important properties of light, which provides a new degree of freedom for the regulation of light field and will produce the new effects and new applications by evolution of optical field and interaction of the light and matter.This paper firstly introduces the basic theory of focusing azimuthally polarized light and the inverse Faraday effect theory. The magnetization field distribution of the azimuthally polarized vortex beams is studied theoretically and numerically.Secondly, the distribution of the magnetization field characteristics of the azimuthally polarized light beam modulated by the amplitude modulator and the spiral phase plate in the 4Pi focusing system is studied. Through the optimal design of amplitude modulator, azimuthally polarized vortex beam can produce single or multiple spherical magnetic spots distribution. The gradient force of single or multiple magnetic spheres on the effect of magnetic particles is simulated. The theory proves that the single or multiple magnetic spheres have the ability to capture the particles stably. Furthermore, a plurality of magnetic spheres can improve the particle capture efficiency.Finally, studying the dynamic characteristics of azimuthally polarized vortex THZ pulse the magnetization field. According to the change of the magnetization field in the same time interval, the change of the transmission speed of the magnetic field can be characterized qualitatively. The transmission speed is slow at the focal point, and the transmission speed is faster in the distance from the focus. The results are conducive to the flexible control of the transmission and acceleration of particles.