Left, SEM images of rib waveguides (up) and gratings (down) on cellulose acetate and silicon respectively. Right, diffraction pattern (up) and laser emission from polymer DFBs (down). Left, SEM images of rib waveguides (up) and gratings (down) on cellulose acetate and silicon respectively. Right, diffraction pattern (up) and laser emission from polymer DFBs (down).