Fig. 1. Evolution of grating bottom pattern from diamond to circle in the fabrication of a two-dimensional grating mask by two-beam orthogonal exposure

Fig. 2. Relationship between bottom contour pattern and light intensity of interference field after two-dimensional grating development. (a) Distribution of light intensities in a single period of two-beam orthogonal exposure; (b) bottom contours of two-dimensional grating with different form factors

Fig. 3. Schematic diagram of two-dimensional grating. (a) Grating use condition; (b) three-dimensional morphology of grating; (c) top view of grating; (d) cross-section of grating

Fig. 4. Different graphic sampling accuracies in FMM. (a) Number of samping point is 32; (b) number of samping point is 128

Fig. 5. Variation in diffraction efficiency of grating with wavelength and incideng angle. (a) Wavelength; (b) incident angle

Fig. 6. Electric field distribution of grating. (a) Schematic diagram of three-dimensional; (b) electric field distribution in x-z plane at 780 nm; (c) electric field distribution in y-z plane at 780 nm; (d) electric field distribution in x-z plane at 791.5 nm

Fig. 7. Tolerances of etching depth and duty cycle. (a) TE polarization; (b) TM polarization

Fig. 8. Tolerances of thickness for Ta₂O₅ and SiO₂ coatings. (a) TE polarization; (b) TM polarization

Fig. 9. Tolerances of duty cycle and sidewall angle. (a) TE polarization; (b) TM polarization

Fig. 10. Traditional design structure. (a) Round table; (b) prism table

Fig. 11. Tolerances of etching depthand duty cycle for round table structure. (a) TE polarization; (b) TM polarization

Fig. 12. Tolerances of etching depthand duty cycle for prism table structure. (a) TE polarization; (b) TM polarization