Study of subwavelength localization of a radiation by forming closely spaced singular lines using of subwavelength features of the dielectric micro-relief

The possibility of formation of closely spaced singular lines using subwavelength details of the dielectric micro-relief is examined. A numerical simulation shows that the diffraction pattern for the subwavelength ridge and groove (size of 0,2l) are drastically different: the ridge shows the focusing properties, and the groove acts as a barrier. Micro-relief with specific combinations of phase steps, corresponding to a phase shift of p, allows to achieve the sub-wavelength localization of radiation (FWHM = 0,36l). Further narrowing the distance between the singular lines leads to loss of energy in the central region and growth of the sidelobes. Simulations were performed using the finite element method, implemented in the Comsol software product.