Beam-Scanning Planar Lens Based on Metal–Dielectric–Metal Waveguide Arrays

Under specific illumination conditions, periodic arrays of metal–dielectric–metal (MDM) waveguides act as uniform optical phased-array antenna where the phase of the radiating optical wave can be controlled by modifying the refractive index distribution of the dielectric material. Based on this property, we propose a planar gradient index MDM-based lens which can transform spherical waves of the transverse-magnetic surface plasmon polariton waves to plane waves with specific beam deflections by adjusting the refractive index configurations. Using numerical simulations based on two-dimensional finite-difference time-domain method, it is confirmed that beam focusing and splitting with multiple dflection angles can also be achieved.