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The concept of the PT-symmetry, originating from the quantum field theory,has been intensively investigated in optics, stimulated by the similaritybetween the Schr\"odinger equation and the paraxial wave equation that governsthe propagation of light in a guiding structure. We go beyond the bounds of theparaxial approximation and demonstrate, using the solution of the Maxwell'sequations for light beams propagating in deeply subwavelength waveguides andperiodic lattices with "balanced" gain and loss, that the PT symmetry may stayunbroken in this setting. Moreover, the PT-symmetry in subwavelength opticalstructures may be restored after being initially broken upon the increase ofgain and loss. Critical gain/loss levels, at which the breakup and subsequentrestoration of the PT symmetry occur, strongly depend on the scale of thestructure.

PT-symmetry in optics beyond the paraxial approximation