Huang Chia-Chien, Sun Te-Chia
Department of Physics, National Chung Hsing University, 145, Xingda Rd., Taichung, 402, Taiwan, ROC.
Institute of Nanoscience, National Chung Hsing University, 145, Xingda Rd., Taichung, 402, Taiwan, ROC.
Sci Rep. 2019 Sep 4;9(1):12756. doi: 10.1038/s41598-019-49186-x.
This paper presents an ultracompact tunable device for power splitting and switching by tuning the Fermi energy level of monolayer patternless graphene underneath a slotted multimode interference (MMI) coupler operating in the mid-infrared, λ = 9-11 μm. By introducing a high-index silicon slot in the central region of the MMI structure, which can significantly shorten the beat length, the proposed device has an approximately 4.5-fold reduction in device length and a two-fold improvement in power transmission compared with conventional MMI couplers without slotting. The device has a footprint of only 0.30 × 0.65 μm (<λ/10), making it the smallest power splitter and switcher. Over the bandwidth of 2 μm, the power transmission of the proposed device is nearly uniform. Extending the operating bandwidth is limited only by the practically achievable Fermi energy of graphene. For the fabrication tolerance, the numerical results show that the relative power variations are lower than 5%, even though the dimension variations are greater than 15%. With its advantages of tunability, compact footprint, and broadband operation, the proposed device is suitable for highly dense photonic integrated circuits.
本文介绍了一种超紧凑型可调谐器件，用于在工作于中红外波段（λ = 9 - 11μm）的开槽多模干涉（MMI）耦合器下方，通过调节无图案单层石墨烯的费米能级来实现功率分配和切换。通过在MMI结构的中心区域引入高折射率硅槽，这可以显著缩短拍长，与无开槽的传统MMI耦合器相比，该器件的长度减少了约4.5倍，功率传输提高了两倍。该器件的占地面积仅为0.30×0.65μm（<λ/10），使其成为最小的功率分配器和切换器。在2μm的带宽范围内，该器件的功率传输几乎是均匀的。扩展工作带宽仅受石墨烯实际可实现的费米能量限制。对于制造公差，数值结果表明，即使尺寸变化大于15%，相对功率变化仍低于5%。由于其可调谐性、紧凑的占地面积和宽带操作的优点，该器件适用于高密度光子集成电路。
