Fig. 1. Schematic of the waveguide superlattices with AGF.

Fig. 2. (a) Band-gap diagram (first two minibands) of a typical straight waveguide array for $a=2.65\mu \mathrm{m}$, $w_1=1\mu \mathrm{m}$, $w_2=0.85\mu \mathrm{m}$, $\mathrm{\Delta }n=0.31$, $\lambda =1.55\mu \mathrm{m}$, and $n_0=1.450$, where the propagation constant is plotted as a function of the Bloch wave number and the shaded regions represent the bands. (b) Ninth-order ($J_9$) and tenth-order ($J_{10}$) Bessel modulation of the first kind. $J_{10}$ and $J_9$ have the same sign in the marked red region.

Fig. 3. Simulated normalized field evolution in (a) normal waveguides, (b) ordinary superlattice, (c) AGF waveguide array, and (d) AGF-enabled superlattice, where gap = 400 nm, $L=200\mu \mathrm{m}$. Schematic top views of the simulated structures are located at the corners of each subimage.

Fig. 4. Simulated crosstalk in the designed waveguide array (gap = 400 nm, $\lambda =700$ to 1700 nm) when (a) fundamental TE mode and (b) fundamental TM mode are launched, respectively. The pink planes correspond to $-28$ and $-25\mathrm{dB}$, respectively.

Fig. 5. (a) The top-view microscope image of the fabricated device on the ${\mathrm{Si}}_3{\mathrm{N}}_4$ platform ($\text{gap}=400\text{n}\mathrm{m}$, $L=200\mu \mathrm{m}$). (b) SEM image of the cross section of a waveguide ($\text{gap}=400\text{n}\mathrm{m}$, $L=200\mu \mathrm{m}$). (c) The top-view microscope image of the fabricated device on the ${\mathrm{Si}}_3{\mathrm{N}}_4$ platform ($\text{gap}=500\text{n}\mathrm{m}$, $L=1\mathrm{mm}$). (d) Experimentally recorded light trajectory in modulated samples for 850 nm.

Fig. 6. (a) Measured transmission spectra of the AGF-enabled superlattice ($\text{gap}=400\text{n}\mathrm{m}$). (b) Measured transmission spectra of the AGF-enabled superlattice ($\text{gap}=500\text{n}\mathrm{m}$). The pink planes correspond to $-24$ and $-28\mathrm{dB}$, respectively.

Fig. 7. Simulated crosstalk for AGF-enabled superlattice with (a) $\mathrm{\Delta }A=-50\mathrm{nm}$ and (b) $\mathrm{\Delta }A=+50\mathrm{nm}$. The pink planes correspond to $-20\mathrm{dB}$.

Fig. 8. Simulated crosstalk for AGF-enabled superlattice that widths of all waveguides (a) increase by 25 nm and (b) decrease by 25 nm. The pink planes correspond to $-20\mathrm{dB}$.

Fig. 9. (a) Measured SNR profiles of the system after transmission through the waveguide array. (b) The bit allocation of 112-Gbit/s DMT signals. Inset: constellations of different subcarriers.