Subdiffraction Focusing Metalens Based on the Depletion of Bessel Beams

Superresolution microscopy is of great interests in modern optics and photonics applications. Subdiffraction focusing lens, that has superresolution focal spot with local spatial frequency greater than the maximum Fourier component, has attracted intensive attentions in past decade, because of the significant capability of unlabeled far-field superresolution. Here, we propose a dielectric subdiffraction focusing metalens based on the depletion of Bessel beams. Different from traditional binary wavefront modulation elements, this metalens is designed according to the reverse engineering of subdiffraction focal field, which is constructed from the depletion of a fundamental Bessel beam. With the independent amplitude and phase control ability of dielectric metasurface, this metalens enables breaking the diffraction limit and can produce a focal spot with full width at half maximum of 0.3λ/NA. This work may provide a platform for the design of integrated and compact photonic devices to control the light propagation dynamics and spin angular momentum associated with circular polarization.