An apparatus and related methods for modulating an electromagnetic radiation beam are described. A composite material is positioned in the path of the radiation beam, the composite material comprising a plurality of commonly oriented metallic first lines spaced apart by less than a wavelength of the radiation beam and a plurality of commonly oriented metallic second lines also spaced apart by less than that wavelength. The second lines are positioned in a crossing arrangement with the first lines, a crosspoint location being defined where each first line crosses each second line. An electrically programmable impedance memory element is positioned at each crosspoint location and is electrically coupled between the first and second lines corresponding to that crosspoint location, each impedance memory element having an electrically programmed state. The composite material modulates the radiation beam according to the electrically programmed states of the impedance memory elements.