Fig. 1. Schematic of photonic crystal heterostructure based on silicon.

Fig. 2. (a) Photonic band diagrams of PhC 1; (b) the photonic band diagrams of PhC 2, where the insert shows the energy band of PhC 2 in Γ－X direction; (c) the first band EFC of PhC 1 under TE polarized light; (d) the fourth band EFC of PhC 2 under TE polarized light (blue lines represent TE mode at the wavelength of 1550 nm); (e) the first band EFC of PhC 1 under TM polarized light; (f) the third band EFC of PhC 2 under TM polarized light (red lines represent TM mode at 1550 nm).

Fig. 3. Electric field intensity distribution of forward transmission and backward transmission at the wavelength of 1550 nm: (a) Forward transmission of TE polarized light; (b) backward transmission of TE polarized light; (c) forward transmission of TM polarized light; (d) backward transmission of TM polarized light.

Fig. 4. Transmittance spectra of heterostructure: (a) TE polarized light, (b) TM polarized light. The grey region represents the asymmetric transmission working wavelength range, where forward transmission is higher than 0.5.

Fig. 5. Schematic of optimization of photonic crystal heterostructure, where the row of photonic lattice is highlighted by the red square is optimized.

Fig. 6. Transmittance spectra of the TE polarized light with different radii of PhC 1 photonic lattice at heterostructure interface: (a) R = 55 nm; (b) R = 65 nm; (c) R = 70 nm; (d) R = 75 nm.