An optical waveguide modulator for modulating an optical beam is described. The modulator includes a substrate and a waveguide formed in or on the substrate. A plurality of conductive membranes which define an array each being effective in a first position to be spaced from the waveguide and located along the waveguide, and in a second position to be closer to or to engage the waveguide so that when in the second position, the optical absorption properties of the waveguide changes.