A method is proposed for reading sub-diffraction-limited recording marks to achieve higher-density optical data storage. We utilize polarization rotation of light reflected from a recording medium owing to the inhomogeneous distribution of the transverse field perpendicular to the polarization direction of focused reading beam. Even if the readout beam simultaneously illuminates several marks, the mark pattern can still be identified by detecting the change in the polarization of the reflected signal light in addition to its intensity. The feasibility of the method was demonstrated by performing a numerical calculation and an experiment with a model recording medium.
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