Efficient extraction of light from a high refractive index silicon waveguide out of a chip is difficult to achieve. An inverse design approach was employed using the particle swarm optimization method to attain a vertical emitting meta-grating coupler with high coupling efficiency in a 220-nm-thick silicon-on-insulator platform. By carefully selecting the figure of merit and appropriately defining parameter space, unique L-shape and U-shape grating elements that boosted the out-of-plane radiation of light were obtained. In addition, a 65.7% (−1.82 dB$-1.82\mathrm{dB}$) outcoupling efficiency and a 60.2% (−2.2 dB$-2.2\mathrm{dB}$) fiber-to-chip vertical coupling efficiency with an 88 nm 3 dB bandwidth were demonstrated by numerical simulation. Considering fabrication constraints, the optimized complex meta-grating coupler was modified to correspond to two etching steps and was then fabricated with a complementary metal-oxide-semiconductor-compatible process. The modified meta-grating coupler exhibited a simulated coupling efficiency of 57.5% (−2.4 dB$-2.4\mathrm{dB}$) with a 74 nm 3-dB bandwidth in the C-band and an experimentally measured coupling efficiency of 38% (−4.2 dB$-4.2\mathrm{dB}$).

中文翻译：

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220 nm 绝缘体上硅平台上硅基高性能垂直发射元光栅耦合器的逆向设计

从芯片中的高折射率硅波导中高效提取光是很难实现的。采用粒子群优化方法的逆向设计方法在 220 nm 厚的绝缘体上硅平台中获得具有高耦合效率的垂直发射元光栅耦合器。通过仔细选择品质因数并适当定义参数空间，获得了独特的 L 形和 U 形光栅元件，可增强光的面外辐射。此外，65.7% ( − 1.82 dB $-1.82\mathrm{dB}$ ) 的输出耦合效率和 60.2% ( − 2.2 dB) $-2.2\mathrm{dB}$) 通过数值模拟证明了具有 88 nm 3 dB 带宽的光纤到芯片垂直耦合效率。考虑到制造限制，优化的复杂元光栅耦合器被修改为对应于两个蚀刻步骤，然后使用互补金属氧化物半导体兼容工艺制造。改进后的元光栅耦合器在 C 波段具有 74 nm 3-dB 带宽，模拟耦合效率为 57.5% ( − 2.4 dB )，实验测量的耦合效率为 38% ( $-2.4\mathrm{dB}$− 4.2 dB $-4.2\mathrm{dB}$ )。