Wu Shengbao, Zhao Zhicheng, Feng Ting, Steve Yao X
Appl Opt. 2020 Feb 10;59(5):1447-1453. doi: 10.1364/AO.383073.
A compact silicon-based cross-slot waveguide (CSW) polarization beam splitter (PBS) utilizing a sandwich-type coupler is proposed. The coupler consists of two identical CSWs separated by a horizontal slot waveguide (HSW), and S-bend sections at each end of the coupling section are introduced to decouple and separate the light. Owing to the strong birefringence of the HSW, the coupling length ratio between two different polarized modes (TE and TM) is adjustable in a suitable range by simply changing the gap width between the CSW and the HSW. The coupling length of the TM mode can be easily made half of that of the TE mode with a proper gap width, which is a favorable condition to realize a short PBS. Then, by making the length of the coupling section equal to the coupling length of the TE mode, the TE and TM modes are split. The PBS has the advantages of a small footprint and a high polarization extinction ratio (PER) and may be useful in the polarization management of a CSW-based on-chip optical system. Numerical results indicate that a PBS of ∼12µ with an insertion loss (IL) of 0.17 (0.53) dB, PER of 24.12 (21.14) dB for the TM (TE) mode is achieved at the wavelength of 1.55 µm, with a bandwidth covering the full C band for keeping >15 and <1.
提出了一种利用三明治型耦合器的紧凑型硅基交叉槽波导（CSW）偏振分束器（PBS）。该耦合器由两个由水平槽波导（HSW）隔开的相同CSW组成，并在耦合段的每一端引入S形弯曲段以解耦和分离光。由于HSW的强双折射，通过简单地改变CSW和HSW之间的间隙宽度，可以在合适的范围内调节两种不同偏振模式（TE和TM）之间的耦合长度比。在适当的间隙宽度下，TM模式的耦合长度可以很容易地制成TE模式耦合长度的一半，这是实现短PBS的有利条件。然后，通过使耦合段的长度等于TE模式的耦合长度，将TE和TM模式分开。该PBS具有占地面积小和偏振消光比（PER）高的优点，可能有助于基于CSW的片上光学系统的偏振管理。数值结果表明，在1.55μm波长下实现了一个约12μm的PBS，其插入损耗（IL）为0.17（0.53）dB，TM（TE）模式的PER为24.12（21.14）dB，带宽覆盖整个C波段，保持>15和<1。
