Fig. 1. Fabrication process of multilayer dielectric pulse compression grating

Fig. 2. MCF polishing principle

Fig. 3. Comparison of grating depth curves

Fig. 4. Grating structure height data distribution

Fig. 5. 3D morphology of grating before and after polishing measured by AFM

Fig. 6. Surface morphologies of unpolished and polished PCG by AFM

Fig. 7. Surface roughness of PCG before and after polishing

Fig. 8. -1st Diffraction Efficiencies （DE） of samples 1 and 2 before and after polishing

Fig. 9. Laser induced damage threshold before and after polishing.