Infrared focusing mirror based on multilevel reflectarray

This contribution shows the first demonstration of a focusing reflectarray working at infrared wavelengths. The principles of design are based on the resonance of sub-wavelength metallic patches, properly sized to produce a given phase shift between the incoming and reflected wave-fronts. The multilevel phase-shifts are arranged following a Fresnel zone scheme. The designed reflectarray is fabricated and tested, showing the expected focusing behaviour.