Bifunctional Broadband Zone Plate for Highly Directive Broadside Emissions and Endfire Radiations

Zone plate reflectors for the highly directive broadside radiations are investigated in this letter, where we show that such a reflector could also function as a lens with endfire emissions when integrated with a dielectric phase compensation layer. More specifically, we employ additional dielectrics to collimate electromagnetic fields radiating through the radial direction of the original zone plate reflector, and obtain well-collimated beams as a lens without degrading the performances of the zone plate as a reflector. We practically implement the proposed design through drilling subwavelength holes with different sizes in a dielectric host medium, and the perforated zone plate demonstrates the functionalities of generating both broadside and endfire radiations in a broadband frequency range.