Sub-wavelength focusing characteristics study of the metalens under oblique incidence
Sub-wavelength focusing lenses are widely used in optical applications such as optical microscopy,imaging,and lithography.The focused optical field with sub-wavelength structure has additional axial aberrations that severely af-fect the quality of optical imaging at oblique incidence.A high numerical aperture(0.970)optical metalens design method is presented,which can simultaneously meet the sub-wavelength tight focusing and broadband operation at oblique inci-dence.Optical field control functions with wide-angle response meta-atoms are used,combined with corrections to the ob-lique incident optical field by aperture stop.The numerical simulation results show that the metalens with 5pm aperture stop,sub-wavelength tight focusing can be achieved within the incidence angle 士30°,and the peak full-width-at-half-maximum range is 0.600～0.885λ.Sub-wavelength focusing is achieved in the incident wavelength range of 550～750nm with an operational bandwidth of 200 nm.
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