A dynamic diffractive structure includes an optical waveguide having a surface, a first transparent electrode coupled to the surface, a chamber formed on the surface, and a nanoscale diffraction grating structure including a plurality of ridges formed on the first transparent electrode and within the chamber and a plurality of channels between adjacent ridges of the plurality of ridges. The dynamic diffractive structure also includes a fluid having an index of refraction disposed within the chamber, a second transparent electrode, and a cover coupled to the chamber. In a first state, the fluid substantially fills the plurality of channels, causing the dynamically actuable diffractive grating to be in an “off” state and in a second state, the fluid is substantially absent from at least a portion of the plurality of channels, causing the dynamically actuable diffractive grating to be in an “on” state and diffract incident light.