Fig. 1. Diffraction efficiency of incident light as a function of wavelength under different states

Fig. 2. Diffraction efficiency of gratings with different grating densities as a function of wavelength

Fig. 3. Diffraction efficiency of gratings with different flare angles as a function of wavelength

Fig. 4. Designed grating groove

Fig. 5. Diffraction efficiency of grating with different platform ratios as a function of wavelength

Fig. 6. Diffraction efficiency of grating with different platform height h as a function of aspect ratio f

Fig. 7. Diffraction efficiency of grating with different platform height h as a function of aspect ratio f

Fig. 8. Crystal alignment flow chart

Fig. 9. Mask patterns for pre-etching processes

Fig. 10. Etched silicon wafer and its microstructure

Fig. 11. Fringe width after etching

Fig. 12. Schematic diagram of mask alignment

Fig. 13. Moire fringes during alignment process

Fig. 14. Grating preparation process. (a) Silicon wafer cleaning; (b) preparation of oxide layer; (c) spin coated photoresist; (d) alignment exposure; (e) development; (f) photoresist pattern transfer; (g) preparation of oxide mask; (h) wet etching; (i) remove the surface mask

Fig. 15. Comparison results of mask expansion ratio for photoresist mask (a) before and (b) after ashing

Fig. 16. Comparison results of grating surface roughness (a) before and (b) after using isopropanol

Fig. 17. AFM test pattern of prepared blazed grating

Fig. 18. Comparison of actual groove shape and designed groove shape

Fig. 19. Comparison results of diffraction efficiencies for designed grating and fabricated grating