Li Chenlei, Zhang Ming, Bowers John E, Dai Daoxin
Opt Lett. 2020 Apr 15;45(8):2259-2262. doi: 10.1364/OL.389207.
An ultra-broadband polarization beam splitter (PBS) with low excess loss (EL) and a high extinction ratio (ER) is proposed and demonstrated for the case with 340 nm thick silicon-on-insulator waveguides. Here the PBS is realized by using cascaded adiabatic dual-core tapers, which consist of a strip core and a subwavelength-grating core. For the designed PBS, which has a 33.6 µm long mode-evolution region, the ELs are ${ \lt }{0.3};{\rm dB}$<0.3dB, and the ERs are ${ \gt }{20};{\rm dB}$>20dB for both TE and TM polarizations in an ultra-broad bandwidth of ${ \gt }{270};{\rm nm}$>270nm (1400-1670 nm) in theory. For the fabricated PBS, the measured bandwidths for achieving ERs of ${\sim}{20}$∼20 and ${\sim}{25};{\rm dB}$∼25dB are 240 and 220 nm, while the 1 dB bandwidth is as large as 230 nm, which are the largest bandwidths reported to date, to the best of our knowledge.
针对厚度为340 nm的绝缘体上硅波导，提出并演示了一种具有低附加损耗（EL）和高消光比（ER）的超宽带偏振分束器（PBS）。在此，PBS通过级联绝热双核锥形实现，其由一个条形芯和一个亚波长光栅芯组成。对于设计的PBS，其模式演化区域长度为33.6 µm，理论上在大于270 nm（1400 - 1670 nm）的超宽带内，TE和TM偏振的EL均小于0.3 dB，ER均大于20 dB。对于制作的PBS，实现约20 dB和约25 dB消光比的测量带宽分别为240 nm和220 nm，而1 dB带宽高达230 nm，据我们所知，这是迄今为止报道的最大带宽。
