Birefringent elements based on femtosecond laser-induced nanogratings

We report on the fabrication of birefringent optical components based on so-called nanogratings. These selforganized nanostructures with sub-wavelength periodicity are formed during femtosecond laser processing of transparent materials, resulting in characteristic birefringent modifications. Nanogratings provide the means for the direct inscription of customized birefringent elements with position-dependent retardation. We present our investigations on the formation process of nanogratings in fused silica and the influence of fabrication parameters, thereby identifying ways to systematically control the structural properties of the gratings. Consequently, we were able to fabricate nanograting-based birefringent elements with specific retardations in bulk fused silica.