Lu Mengjia, Deng Chunyu, Sun Yu, Wang Dongyu, Huang Lei, Liu Pengcheng, Lin Dongdong, Cheng Wei, Hu Guohua, Lin Tong, Yun Binfeng, Cui Yiping
Opt Express. 2022 Jul 4;30(14):24655-24666. doi: 10.1364/OE.462554.
A compact and broadband silicon mode-order converter (MOC) scheme by employing reciprocal mode evolution between asymmetric input/output taper and bricked subwavelength gratings (BSWG) is proposed. In the proposed MOC, a quasi-TE mode is generated in the BSWG region, which can be regarded as an effective bridge between the two TE modes to be converted. Flexible mode conversion can be realized by only choosing appropriate structure parameters for specific mode transitions between input/output modes and the quasi-TE mode. By combing 3D finite difference time domain (FDTD) and particle swarm optimization (PSO) method, TE-TE and TE-TE MOCs are optimal designed, which can efficiently convert TE mode to TE and TE modes with lengths of 9.39 µm and 11.27 µm, respectively. Results show that the insertion losses of <1 dB and crosstalk of <-15 dB are achieved for both TE-TE and TE-TE MOCs, the corresponding working bandwidth are 128 nm (1511∼1639 nm) and 126 nm (1527∼1653 nm), respectively. Additionally, the MOCs can be fabricated with only single etch step with minimum feature size of 145 nm.
提出了一种紧凑且宽带的硅模式阶数转换器（MOC）方案，该方案利用非对称输入/输出锥形与砖形亚波长光栅（BSWG）之间的互易模式演化。在所提出的MOC中，在BSWG区域产生一个准TE模式，该模式可被视为待转换的两种TE模式之间的有效桥梁。通过仅为输入/输出模式与准TE模式之间的特定模式转换选择合适的结构参数，即可实现灵活的模式转换。通过结合三维时域有限差分（FDTD）和粒子群优化（PSO）方法，对TE-TE和TE-TE MOC进行了优化设计，它们可分别将TE模式高效转换为长度为9.39 µm的TE模式和长度为11.27 µm的TE模式。结果表明，TE-TE和TE-TE MOC的插入损耗均<1 dB，串扰均<-15 dB，相应的工作带宽分别为128 nm（1511∼1639 nm）和126 nm（1527∼1653 nm）。此外，MOC仅需单步蚀刻即可制造，最小特征尺寸为145 nm。
