Fig. 1. The structure and diffraction of phase-type photon sieve based on GO

Fig. 2. Electric field intensity distribution of phase-type photonic sieve

Fig. 3. The change of focusing effect of photon sieve with refractive index difference

Fig. 4. Direct writing process and thickness of GO thin film

Fig. 5. Changes of n and k of rGO under different laser power

Fig. 6. Morphology of photon sieves prepared by different laser power

Fig. 7. Optical path diagram of photon sieve focusing

Fig. 8. Transmission of diffraction light field of photon sieve

Fig. 9. Change of light spot diameter along the optical axis沿光轴光斑直径的变化

Fig. 10. Changes in focal length and diffraction efficiency of the photon sieve prepared with different laser power