We theoretically show the effect of a microwave field on the induced focusing of an optical weak probe beam by a copropagating nonuniform control beam in an electromagnetically induced transparency medium. Our numerical simulation shows that, in the presence of a microwave field, probe beam focusing is phase-sensitive and the focused beam size is reduced by 70% of its initial width. In contrast, in the absence of a microwave field, the reduction in the size of the transmitted probe beam is only

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... about 30%. This approach is also successfully applied to the focusing of the diffraction-limited structure of the probe beam.