The optic axes of the different carbon nanotubes (with direction of the beams) are indicated by the arrows. For the double axes devices, the axes' plane is shown; initially, field vectors (arrows orthogonal to the axes) are polarized in this plane. The out of plane arrows indicate the rotated (for the angles α and β) field vectors of the outgoing beams. The position of the axes and the relative values of α and β depend on symmetry group of the tube.