Ultrashort pulse-induced nanogratings: Temperature stable optically active phase elements

We present femtosecond direct written optical components exhibiting circular birefringence. Based on tightly focused ultrashort laser pulses in the bulk of fused silica, self-organized modifications, so called nanogratings can be induced [1]. Due to their anisotropic structure and sub-wavelength periodicity, these nanogratings show a strong form-birefringence. Emerging after several laser pulses they are always oriented perpendicular to the laser polarization. So by combing the tunable orientation of the nanogratings with the outstating three-dimensional writing ability allows for the fabrication of almost arbitrary phase elements [2,3].