Near field focusing by edge diffraction

Spherical microparticles have the ability for nonresonant focusing of light in the near field zone, forming nanojet (NJ) beams. Arbitrary-shaped microstructures, with wave-length-scale dimensions, may offer similar functionality with lower fabrication complexity. The focusing properties are ruled by the edge diffraction phenomenon. The diffraction of light on the edge of a dielectric microstructure forms a tilted focused beam whose deviation angle depends on the index ratio between the structure material and host medium. The beam geometry and field intensity enhancement can be tuned by varying the curvature of the edge line. Interference of edge diffracted waves from different segments of the edge line creates a condensed beam in the nearfield zone, the photonic nanojet.

Near field focusing by edge diffraction“, A. Boriskin, V. Drazic, R. Keating, M. Damghanian, O. Shramkova, L. Blondé. Optics Letters, vol. 43, Issue 16, pp. 4053-4056 (2018)

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Localized photonic jets generated by step-like dielectric microstructures

 In this contribution we reveal how the step-like topology of a microstructure can contribute to the formation of a single high-intensity nanojet (NJ) beam located on its axis of symmetry. The proposed method for generating condensed optical NJ beams relies on the complex electromagnetic phenomenon associated with the light diffraction on the edges of step-like dielectric microstructures embedded in a host medium with lower refractive index. The possibility of NJ beam intensification in the near zone of such microstructure illuminated by a plane wave is demonstrated and explained by the recombination of multiple NJ beams associated with different edges or edge segments of the step-like microlens. We demonstrate that by changing materials of the layers we can intensify the NJ beam. We examine the dependence of the generated beam on the step size, shape and material.

Localized photonic jets generated by step-like dielectric microstructures“, O. Shramkova, V. Drazic, M. Damghanian, A. Boriskin, V. Allié, L. Blondé, International Conference on Transparent Optical Networks, 1-5 July 2018, Bucharest, Romania.

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