An optical structure includes a substrate, a circular grating resonator (CGR) formed on the substrate, the CGR including a center disc and a plurality of concentric rings spaced from one another; an input planar waveguide and an output planar waveguide each formed on the substrate, the input planar waveguide and the output planar waveguide optically coupled to the CGR; and an electrode pair, formed on the substrate, coplanar with the input and output planar waveguides, the electrode pair comprising an electrically conductive material in contact with opposing ends of the center disc of the CGR so as to render the CGR capable of electro-optical control.