Dielectric metalenses with engineered point spread function

Abstract

High-index silicon nanoblocks support excitation of both electric and magnetic resonance modes at telecommunication wavelengths. At frequencies where both electric and magnetic resonance modes are excited simultaneously, changing the geometrical dimensions of the silicon cubes creates a 2π full span over the phase of the transmitted light in different amplitude ranges. We take advantage of the additional power-flux modulation of the scattered signal to focus the incident light with desired full width at half maximum (FWHM) and side lobe levels (SLLs) in both the lateral and axial directions. By implementing proper amplitude filters within the telecommunication working wavelength (1.55 μm), a FWHM less than half of the wavelength (0.42λ_eff) and apodization with nearly faded SLLs are achievable. Our approach introduced in this paper provides a new way to design high efficiency metalenses with desired FWHM and SLL of focal spot.