Generation of pure longitudinal magnetization needle with tunable longitudinal depth by focusing azimuthally polarized beams

Abstract

Based on the inverse Faraday effect, a pure longitudinal magnetization with a tunable longitudinal depth and a high corresponding aspect ratio can be generated by tightly focusing a narrow annulus of azimuthally polarized beam on optomagnetic materials. Theoretical calculation demonstrates that the induced magnetization has the same longitudinal depth as the beam needle, but with different distributions. The magnetization needle can be tunable by changing the value of the angular thickness ∆θ, and a long longitudinal depth (91.4λ) can be achieved.