A generator of duality modulated radiation and a corresponding method for its use. The generator depletes or enriches the proportion of energy relative to the wave intensity of a beam. Duality modulation is achieved using a single input beam that is incident on a diffractive grating. For a selected grating structure, the angle of incidence, the wavelength of the input beam and the periodicity of the grating are selected to achieve a desired duality modulation in a diffracted output beam.