Higher-order mode conversion plays a vital role in on-chip multimode applications. Here, we propose an efficient silicon-based higher-order mode conversion scheme that can achieve the mode-order conversion from ${{\rm{TE}}_0}$ to ${{\rm{TE}}_1}$ (${{\rm{TE}}_0} {-} {{\rm{TE}}_1}$) mode and from ${{\rm{TE}}_0}$ to ${{\rm{TE}}_2}$ (${{\rm{TE}}_0} {-} {{\rm{TE}}_2}$) mode, respectively. These mode conversion functions are realized by etching subwavelength grating (SWG) slots on a silicon waveguide, where the design of the SWG slot pattern matches with the required ${{\rm{TE}}_1}$ (${{\rm{TE}}_2}$) higher-order mode. According to the calculations, the mode conversion length is only 3.3 µm (4.32 µm) with the mode conversion efficiency (CE) 92.1% (95.6%), mode crosstalk (CT) ${-}{17.5}\;{\rm{dB}}$ (${-}{16.7}\;{\rm{dB}}$), and insertion loss 0.65 dB (0.5 dB) for the ${{\rm{TE}}_0} {-} {{\rm{TE}}_1}$ (${{\rm{TE}}_0} {-} {{\rm{TE}}_2}$) mode converter at $\lambda = {1.55}\;{\rm{\unicode{x00B5}{\rm m}}}$. Moreover, device bandwidths over 110 nm (${\rm{CE}} \gt {{90}}\%$ and ${\rm{CT}} \lt - {{15}}\;{\rm{dB}}$) and other higher-order mode conversions can also be achieved using the proposed scheme (e.g., ${{\rm{TE}}_0} {-} {{\rm{TE}}_3}$ and ${{\rm{TE}}_0} {-} {{\rm{TE}}_4}$ mode converters). We believe such a device scheme would help increase the transmission capacity of on-chip multimode multiplexing transmissions by leveraging more mode channels.

中文翻译：

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基于亚波长光栅槽的高效硅基高阶模式转换器

高阶模式转换在片上多模应用中起着至关重要的作用。在这里，我们提出了一种高效的基于硅的高阶模式转换方案，可以实现从${{\rm{TE}}_0}$到${{\rm{TE}}_1}$ ( ${{\rm{TE}}_0} {-} {{\rm{TE}}_1}$ ) 模式以及从${{\rm{TE}}_0}$到${{\rm{TE} }_2}$ ( ${{\rm{TE}}_0} {-} {{\rm{TE}}_2}$ ) 模式。这些模式转换功能是通过在硅波导上蚀刻亚波长光栅 (SWG) 槽来实现的，其中 SWG 槽图案的设计与所需的${{\rm{TE}}_1}$ ( ${{\rm{ TE}}_2}$) 高阶模式。根据计算，模式转换长度仅为 3.3 µm (4.32 µm)，模式转换效率 (CE) 92.1% (95.6%)，模式串扰 (CT) ${-}{17.5}\;{\rm{ dB}}$ ( ${-}{16.7}\;{\rm{dB}}$ )，${{\rm{TE}}_0} {-} { 的插入损耗为 0.65 dB (0.5 dB) {\rm{TE}}_1}$ ( ${{\rm{TE}}_0} {-} {{\rm{TE}}_2}$ ) 模式转换器在$\lambda = {1.55}\;{ \rm{\unicode{x00B5}{\rm m}}}​​$。此外，设备带宽超过 110 nm ( ${\rm{CE}} \gt {{90}}\%$和${\rm{CT}} \lt - {{15}}\;{\rm{dB }}$ ) 和其他高阶模式转换也可以使用建议的方案来实现（例如，${{\rm{TE}}_0} {-} {{\rm{TE}}_3}$和${{\rm{TE}}_0} {-} {{\rm{TE}}_4}$模式转换器）。我们相信这样的设备方案将有助于通过利用更多模式通道来提高片上多模复用传输的传输容量。