基于硅基波导偏振无关光分束器的研究

Research on polarization-independent optical beam splitter based on silicon-based waveguides

本文提出一种基于硅基波导的偏振无关分束器,该器件由对称的定向耦合结构和亚波长结构组成。根据耦合模理论,在传统的定向耦合结构中,TM模的耦合强度强于TE模的耦合强度,难以实现偏振无关分束。在耦合区域增加亚波长结构,能够在增强TE模的耦合强度的同时减弱TM模的耦合强度,使得TE模和TM模的耦合强度相等。因此通过调节定向耦合结构和亚波长结构的相关参数,能够实现偏振无关分束。采用时域有限差分法(FDTD)进行仿真分析,结果表明:该器件可以实现1550nm波长的偏振无关分束,TE模的额外损耗为0.27dB,TM模的额外损耗为0.55dB,器件的耦合区域长度为5.48μm,带宽约为25nm。该器件具有尺寸小,结构简单,易于集成的优点。

In this paper,a polarization independent beam splitter basedon silicon based waveguide is proposed.The deice consists of a symmetric directional coupling structure and a sub-wavelength structure.Accordoing to the coupled mode theory,the coupling strength of the TM mode is stronger than the coupling strength of the TE mode in a traditional directional coupling structure,and it is difficult to achieve polarization independent beam splitting.By using the subwavelength structure in the coupling region,the coupling strength is enhanced for TE mode and is weakened for TM mode,so that the coupling strength could be equivalent between TE and TM modes.Therefore,polarization independent beam splitting can be achieved by adjusting the parameters of the directional coupling structue and the sub-wavelength structure.The time domain finite difference method(FDTD) is used for simulation analysis.The results show that the device can achieve polarization independent beam splitting at 1 550 nm.The excess loss of the TE mode is 0.27 dB,and the excess loss of the TM mode is 0.55 dB.The coupling region length of the device is 5.48 μm,and the bandwidth is about 25 nm.The device has the advantages of small size,simple structure and easy integration.