Fig. 1. Double-cone interference model. (a) Front view; (b) top view

Fig. 2. Photonic structures and period pictures formed when the inter cone angle is increasing and the incremental angle is Δθ=10°. (a) Photonic structure when θ=20°; (b) photonic structure when θ=30°; (c) photonic structure when θ=40°; (d) period picture when θ=20°; (e) period picture when θ=30°; (f) period picture when θ=40°

Fig. 3. Photonic structure diagrams obtained when the incremental angle Δθ is increasing and the inner cone angle θ=30°. (a) Δθ=2°; (b) Δθ=6°; (c) Δθ=10°

Fig. 4. Photonic structures obtained by changing the intensities of inner and the outer cone beams. (a) I_in=1.5, I_out=1; (b) I_in=2, I_out=1; (c) I_in=1, I_out=1.5; (d) I_in=1, I_out=2

Fig. 5. Optical lattice distribution when the intensities of the inner and outer cone beams are different

Fig. 6. Photonic structures formed under different linear polarizations of inner and outer cone beams. (a) Full view; (b) partially enlarged detail

Fig. 7. Results of original cell of double-period gradient photonic structure processed by Fourier transform. (a) Three-dimensional intensity; (b) full width at half maximum of focal spot