Fig. 1. Model of generalized Snell's law of refraction

Fig. 2. Three-dimensional model of dielectric metalens

Fig. 3. The phase delay and transmittance of the dielectric unit structure as a function of width d

Fig. 4. Distribution of ideal phase and unit structure diameter of the dielectric metalens

Fig. 5. Phase distributions of dielectric metalens

Fig. 6. Distribution of electric field intensity and optical field in dielectric metalens

Fig. 7. Structure of beam expander and beam reducer（substrate facing inwards）

Fig. 8. Distribution of electric field intensity and phase of 2-fold and 4-fold beam expander

Fig. 9. Distribution of intensity and phase of the outgoing beams from 2-fold and 4-fold beam expanders

Fig. 10. Distribution of electric field intensity and phase of 2-fold and 4-fold beam reducers

Fig. 11. Distribution of intensity and phase of the outgoing beams from 2-fold and 4-fold beam reducers

Fig. 12. Distribution of electric field intensity and phase of 2-fold beam expander and beam reducer for 2% and 5% wavelength change.

Fig. 13. Distributions of electric field intensity and phase of 2-fold beam expander and beam reducer when the incident angle is deflected by 0.5° and 1°