Three-dimensional grating device includes two (crossed) diffraction gratings, exhibits diffraction efficiency substantially independent of the incident polarization inside an optical communication spectral window from 1.5-1.6 μm. The gratings are characterized by different periods in two directions, chosen to support only one dispersive diffraction order in addition to the zero-(specular) order. Gratings may be orthogonal. Exemplary grating profiles include but are not limited to sinusoidal and truncated pyramidal (trapezoidal) profiles. A method for diffracting polarization independent light with 90% or higher efficiency. Applications include various wavelength control devices particularly useful in telecommunications.