Magnetic Field Induced by Various Input Beam Polarizations in All-Optical Magnetic Recording

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In this work, we investigate the role of the input optical beam polarization on the resulting magnetic field generated for applications like all-optical magnetic recording (AOMR). We consider two mechanisms by which a laser source gives rise to a magnetic field: the inverse Faraday effect and an additional mechanism, referred to as optically-induced spin--orbit coupling, which is especially relevant under the very large electrical field associated with ultrashort laser pulse excitation. We compare the direction, magnitude, and spatial extent of the induced magnetic field for both mechanisms. It is found that circular polarization, which generates a strong magnetic field mainly perpendicular to the medium through the inverse Faraday effect, is well-suited to data storage applications. Azimuthal polarization is also favorable, as it results in a purely perpendicular magnetic field, which in this case is solely due to optically-induced spin--orbit coupling. The numerical examples considered here are based on the pulsed titanium--sapphire laser excitation of a GdFeCo medium, as described in typical AOMR experiments.
2011-09-25