By leveraging cross-like hybrid plasmonic waveguides (HPWs) and subwavelength gratings, a silicon-based ultracompact ${{\rm{TE}}_0}$- and ${{\rm{TE}}_1}$-${\rm{pass}}/{{\rm{TM}}_0}$- and ${{\rm{TM}}_1}$-stop dual-mode polarizer for 1.55/2 µm dual-wavelength is proposed and analyzed in detail. The HPWs are located above the bottom Si waveguide to form a hybrid plasmonic silicon nitride waveguide (HPSNW), in which the ${{\rm{TE}}_0}/{{\rm{TE}}_1}$ mode is well supported in the bottom Si layer while the ${{\rm{TM}}_0}/{{\rm{TM}}_1}$ mode is confined in the ${\rm{Si}}{{\rm{O}}_2}/{\rm{S}}{{\rm{i}}_3}{{\rm{N}}_4}$ layer of the HPSNW and thus sees high absorption loss at 1.55/2 µm. Accordingly, the ${{\rm{TE}}_0}/{{\rm{TE}}_1}$ mode at 1.55/2 µm can directly pass through the device once it is transited from input waveguide to the HPSNW. In contrast, the ${{\rm{TM}}_0}/{{\rm{TM}}_1}$ mode at 1.55/2 µm suffers from great mode radiation and mode attenuation, respectively, caused by the modal mismatch and metal absorption, leading to mode blocking. Therefore, a polarizer with dual-mode/dual-wavelength operation is realized for the first time, to the best of our knowledge. Numerical results show that the proposed polarizer has an insertion loss (IL) of 0.37 dB/0.29 dB for the ${{\rm{TE}}_0}/{{\rm{TE}}_1}$ mode and an extinction ratio (ER) of 17.3 dB/29.7 dB for the ${{\rm{TM}}_0}/{{\rm{TM}}_1}$ mode at 1.55 µm (an IL of 0.42 dB/0.76 dB for the ${{\rm{TE}}_0}/{{\rm{TE}}_1}$ mode and an ER of 33.1 dB/23.3 dB for the ${{\rm{TM}}_0}/{{\rm{TM}}_1}$ mode at 2 µm) in an ultracompact length of 6.5 µm. The operating bandwidth is up to 630 nm when the ER is over 18.5 dB/19.7 dB and the IL is below 0.52 dB/1 dB for fundamental/first-order mode, indicating an ultrabroadband operation. Additionally, fabrication tolerances of the proposed device are investigated, and electric field evolution is also illustrated.

中文翻译：

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使用基于硅的十字形混合等离子体激元波导，用于1.55 / 2 µm双波长的超紧凑型TE ₀和TE ₁ pass / TM ₀和TM ₁停止双模偏振器

通过利用十字形混合等离子波导（HPW）和亚波长光栅，可以制造出基于硅的超紧凑型$ {{\ rm {TE}} _ 0} $ -和$ {{\ rm {TE}} _ 1} $ - $ {\提出并分析了用于1.55 / 2 µm双波长的rm {pass}} / {{\ rm {TM}} _ 0} $ -和$ {{\ rm {TM}} _ 1} $停止双模偏振器详情。HPW位于底部Si波导上方以形成混合等离子体氮化硅波导（HPSNW），其中$ {{\ rm {TE}} _ 0} / {{\ rm {TE}} _ 1} $模式很好$ {{\ rm {Si}} {{\ rm {O）限制在底部Si层中，而$ {{\ rm {TM}} _ 0} / {{\ rm {TM}} _ 1} $模式则被限制在$ {\ rm {Si}} {{\ rm {O }} _ 2} / {\ rm {S}} {{\ rm {i}} _ 3} {{\ rm {N}} _ 4} $在HPSNW的第二层，因此在1.55 / 2 µm处吸收损耗很高。因此，一旦它从输入波导传输到HPSNW，1.55 / 2 µm的$ {{\ rm {TE}} _ 0} / {{\ rm {TE}} _ 1} $模式就可以直接通过该设备。相反，在1.55 / 2 µm的$ {{\ rm {TM}} _ 0} / {{\ rm {TM}} _ 1} $模式由于模态不匹配和金属吸收，导致模式阻塞。因此，据我们所知，这是首次实现具有双模/双波长操作的偏振器。数值结果表明，在$ {{\ rm {TE}} _ 0} / {{\ rm {TE}} _ 1} $模式下，所建议的偏振片的插入损耗（IL）为0.37 dB / 0.29 dB，消光比为（ER）为17.3 dB / 29.7 dB$ {{\ rm {TM}} _ 0} / {{\ rm {TM}} _ 1} $模式为1.55 µm（$ {{\ rm {TE}} _ 0} /的IL为0.42 dB / 0.76 dB {{\ rm {TE}} _ 1} $模式，在2 µm的$ {{\ rm {TM}} _ 0} / {{\ rm {TM}} _ 1} $模式下的ER为33.1 dB / 23.3 dB ）的超紧凑长度为6.5 µm。对于基频/一阶模式，当ER超过18.5 dB / 19.7 dB且IL低于0.52 dB / 1 dB时，工作带宽可达630 nm，这表明超宽带工作。另外，研究了所提出的装置的制造公差，并且还示出了电场演化。