Optical couplers with different power splitting ratios are essential building blocks in photonic integrated circuits. We theoretically and experimentally demonstrate a broadband and fabrication-tolerant $1\times 2$ integrated optical coupler with an arbitrary splitting ratio, based on a mode converter (MC). The MC converts the input mode into a targeted output mode with a desired power distribution, which determines the power splitting ratio at outputs. The geometry of the MC is engineered and optimized by using the particle swarm optimization algorithm combined with the finite-difference time-domain method. Couplers with 10/90, 20/80, 30/70, 40/60, and 50/50 splitting ratios are designed and fabricated on the silicon-on-insulator platform as representatives, with footprints smaller than $2.75~\mu $ m $\times 18.41~\mu $ m. The experimental results show that the ±1 dB bandwidths of these devices are greater than 42 nm around 1550 nm, and the average insertion losses are less than 0.65 dB.

中文翻译：

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基于模式转换器的任意分光比集成光耦合器

具有不同功率分配比的光耦合器是光子集成电路中必不可少的组成部分。我们在理论上和实验上证明了宽带和制造容忍 $1\乘以2$ 基于模式转换器 (MC) 的具有任意分光比的集成光耦合器。MC 将输入模式转换为具有所需功率分配的目标输出模式，这决定了输出端的功率分配比。MC 的几何结构是通过使用粒子群优化算法结合有限差分时域方法来设计和优化的。具有10/90、20/80、30/70、40/60和50/50分光比的耦合器作为代表在绝缘体上硅平台上设计和制造，占地面积小于 $2.75~\mu $ 米 $\times 18.41~\mu $ 米。实验结果表明，这些器件的±1 dB带宽在1550 nm附近大于42 nm，平均插入损耗小于0.65 dB。