(Peer-Reviewed) An ultra-compact polarization-insensitive slot-strip mode converter
Zihan Tao 陶子涵 ¹, Bo Wang 王博 ¹, Bowen Bai 白博文 ¹, Ruixuan Chen 陈睿轩 ¹, Haowen Shu 舒浩文 ¹, Xuguang Zhang 张绪光 ¹, Xingjun Wang 王兴军 ¹ ² ³ ⁴
¹ State Key Laboratory of Advanced Optical Communication Systems and Networks, School of Electronics, Peking University, Beijing 100871, China
中国 北京 北京大学电子学院 区域光纤通信网与新型光通信系统国家重点实验室
² Frontier Science Center for Nano-Optoelectronics, Peking University, Beijing 100871, China
中国 北京 北京大学纳光电子前沿科学中心
³ Peking University Yangtze Delta Institute of Optoelectronics, Nantong 226010, China
中国 南通 北京大学长三角光电科学研究院
⁴ Peng Cheng Laboratory, Shenzhen 518055, China
中国 深圳 鹏城实验室
Integrated waveguides with slot structures have attracted increasing attention due to their advantages of tight mode confinement and strong light-matter interaction. Although extensively studied, the issue of mode mismatch with other strip waveguide-based optical devices is a huge challenge that prevents integrated waveguides from being widely utilized in large-scale photonic-based circuits.
In this paper, we demonstrate an ultra-compact low-loss slot-strip converter with polarization insensitivity based on the multimode interference (MMI) effect. Sleek sinusoidal profiles are adopted to allow for smooth connection between the slot and strip waveguide, resulting reflection reduction. By manipulating the MMI effect with structure optimization, the self-imaging positions of the TE0 and TM0 modes are aligned with minimized footprint, leading to low-loss transmission for both polarizations.
The measurement results show that high coupling efficiencies of − 0.40 and − 0.64 dB are achieved for TE0 and TM0 polarizations, respectively. The device has dimensions as small as 1.1 μm × 1.2 μm and composed of factory-available structures. The above characteristics of our proposed compact slot-strip converter makes it a promising device for future deployment in multi-functional integrated photonics systems.