Twisting Polarization‐Tunable Subdiffraction‐Limited Magnetization through Vectorial Beam Coupling

Abstract

Light-induced switching and manipulation of the magnetization in magneto-optical (MO) materials has enjoyed continuous growing interests due to its potential alluring applications, such as all-optical magnetic recording/storage, [1][2][3][4] magnetic resonance microscopy, [5,6] atom trapping, [7,8] and magnetic holography, [9,10] among other feats. In particular, according to the prediction by International Data Corporation, the total data amount generated globally will reach up to 160ZB (1ZB ¼ 10 12 GB) by the year 2025. [11,12] Such a vast quantity of data elicits an urge to develop bran-new magnetization-based storage technologies. In these contexts, the inverse Faraday effect (IFE) first pioneered in the 1960s has revived as a mainstream leading mechanism giving insights into diverse optomagnetic phenomena, [13][14][15] principally because the light fields tailored either by amplitude/ phase/polarization modulator or by spin/ orbital angular momentum generator could couple strongly with the engineered magnetic systems. [16][17][18][19][20][21] Whereupon a variety of light-triggered subdiffraction-scale versatile magnetization fields with tunable polarization orientations and exotic spatial textures can be achieved by leveraging the canonical IFE, which holds the key for most applications, especially for high-density and low-energy consumption optomagnetic storage. Unlike the circularly polarized beam excitation, [22,23] the well-engineered vectorial beams under tight focusing are able to produce not only purely longitudinal subdiffractionlimited magnetization but also high-purity transverse magnetization, [24,25] which would foster vast opportunities for

Near-Field Behaviors of Internal Energy Flows of Free-Space Electromagnetic Waves Induced by Electric Point Dipoles

“…(d) A circular dipole p with its dipole axis lying on the horizontal plane leads to a filled solid cone of higher values of DoCP.  ○ When a magneto-optical (MO) material, say, a plasmonic scatterer [5,22], with a certain magnetic susceptibility is passively immersed in an EM field, a static magnetization proportional to * E E ×   is induced on that material by the EM field [13,19,20,32,33]. This inverse Faraday effect is distinct from the 'direct' Faraday effect, where a magnetic field serves as an excitation agent [34].…”

“…On the origin lies a primary electric poi linear dipole p with its dipole axis lying para tapered cylindrical surface designating higher val (d) A circular dipole p with its dipole axis lyi cone of higher values of DoCP.  ○ When a magneto-optical (MO) materia certain magnetic susceptibility is passiv magnetization proportional to 19,20,32,33]. This inverse Faraday effect where a magnetic field serves as an exc…”

“…Resultan are largely accompanied by the local en stays forward-directed in the far fiel normally carry any vortical feature. W vortical features are associated with int for instance, non-paraxial counter-prop an incident wave and a scattered wave [13,19,20,32,33]. This inverse Faraday where a magnetic field serves as a…”

“…such as nanoscale gratings [19]. Here, EM waves play crucial roles in a generation, transport, switching [20], and detection [21]. Suppose that → E, → H are electric and magnetic field vectors as solutions to the Maxwell equa-Optics 2022, 3 tions over a source-free (i.e., with neither electric charges nor electric currents) medium [22].…”

5D Opto‐Magnetization Endowed by Physics‐Enhanced Deep Learning

“…[ 26 ] In addition to the elementary engineering of magnetization structure, tailoring multifarious magnetization orientation is manifested as an additional reconfigurable dimension, thereby contributing to the further reinforcement of magnetic memory capacity. Together, a plethora of magnetization structures with certain magnetization orientations, including a single in‐plane magnetization spot, [ 27 ] transverse magnetization spot arrays, [ 28 ] magnetization spot or needle (arrays) with steerable 3D) orientation [ 29–31 ] and twist‐controllable magnetization orientation [ 32 ] have been accessible by tightly focusing the encoded vectorial beams onto the isotropic MO film. To achieve such magnetization structures with diverse orientations, the designing manners such as the reversing electric dipoles, [ 31 ] raytracing models (RMs), [ 28,30 ] and axially symmetrical destruction [ 29 ] are implemented.…”