In one general aspect, a tunable electromagnetic metamaterial as described
herein includes a substrate and an array of split ring resonators formed
on the substrate. At least one of the split ring resonators is a
capacitively tuned split ring resonator. The capacitively tuned split
ring resonator includes a structure having a gap and is formed of an
electrically conductive material. The capacitively tuned split ring
resonator also includes a region of photo-capacitive material formed in
close proximity to the structure such that the capacitance of the
metamaterial is changed when illuminated by controlling electromagnetic
radiation having a selected range of wavelengths.