Tunable Magnetization Chains Induced With Annular Parabolic Mirrors

Abstract

Based on the inverse Faraday effect, tunable light-induced magnetization chains are investigated by focusing narrow annular azimuthally polarized vortex beams with a 4 $\pi$ focusing system composed of double annular parabolic mirrors. Using Richards–Wolf vector diffraction theory, approximate analytical expressions of all parameters of the magnetization chains are theoretically calculated, realizing that all parameters are tunable. The calculated results show that the parameters are independent of the amplitude distribution function of the incident beam and the apodization factor of the focusing system. Hence, different kinds of long (about $100\lambda$ ) chains with sub-wavelength lateral size can be achieved by adjusting the central angular position, the angular width, and the phase difference of two counter-propagating incident beams. Compared with lenses, parabolic mirrors can generate multi-needle fields that lenses cannot.