Polarization-independent two-dimensional diffraction metal-dielectric grating

Two-dimensional (2D) diffraction gratings have been developed rapidly in several growing areas of research, but most of them were polarization sensitive with limitations toward practical applications. We report a 2D diffraction grating solution for achieving polarization-independent high efficiency property. The grating was designed and fabricated based on thin-film coatings, orthogonally lithography, and ion-beam etching technology. The measured average (−1, 0) order reflective diffraction efficiency (DE) is 74.8% (p-polarization) and 68.2% (s-polarization) from 770 nm to 790 nm and the lowest difference of DE between two polarizations is 0.593% at 785.5 nm incident wavelength of our sample.