Single-Chip Optical Single-Sideband Modulator Realized with Si Photonic-Electronic Integrated Circuit Technology
The left figure shows the block diagram of the optical single-sideband modulator. It contains ring modulators, multi-mode interferometers, and a 30-GHz quadrature hybrid coupler. The right figure shows a photograph of the modulator produced with IHP's photonic BiCMOS technology.
Silicon (Si) photonics is a disruptive technology that provides photonic integrated circuit solutions for various demanding applications. The powerful Si integrated circuit fabrication technology for the implementation of photonic devices is applied to realize higher-performance photonic circuits and systems, which has larger degree of integration and higher cost-effectiveness with discrete photonic devices and/or III-V semiconductor technology. Furthermore, the same Si platform and fabrication steps can be used for the implementation of new hardware configurations that contain both photonic and electronic components on a single Si chip.
In a paper published in Photonics Research, Volume 6, No. 1, 2017 (B.-M. Yu et al., Single-chip Si optical single-sideband modulator), researchers from Yonsei University in South Korea and the Innovations for High Performance Microelectronics (IHP) in Germany demonstrated the possibilities of photonic and electronic integration technology. They successfully developed a monolithic Si optical single-sideband (OSSB) modulator operating at 30 GHz. Unlike conventional optical modulators that produce double sidebands, an OSSB modulator produces only one sideband, and it is a key component for radio-over-fiber technology. When the high-frequency electrical signals are transmitted in the optical domain over the fiber, the degradations due to the loss and the interference of many demanding wireless applications can be avoided. In order to realize the OSSB modulator, signal-processing both in the electrical and the optical domains is required. Up until now, this has been performed by separate electrical and optical components, which makes the resulting OSSB modulator device bulky and expensive. Using IHP’s photonic BiCMOS fabrication technology to produce high-performance monolithic Si photonic devices as well as BiCMOS circuits on the same wafer, researchers at Yonsei University and IHP incorporated all required electrical and optical signal-processing functions into a single Si chip. The resulting OSSB modulator achieves high performance, small size, and improved cost-effectiveness. To summarize, a function that conventionally requires a whole ensemble of instruments has been successfully realized with a single Si chip.
Prof. Woo-Young Choi at Yonsei University, the corresponding author of the paper, believes that this work clearly demonstrates the potential of Si photonics and electronic integration technology, and opens the door to many exciting new applications in which various functions requiring both photonics and electronics are implemented in a single chip.
用硅基光电子集成技术实现单片光学单边带调制器
左图：光学单边带调制器的结构示意图，包含了微环调制器、多模干涉仪以及30 GHz正交混合耦合器。右图：用IHP光子BiCMOS技术生产的调制器照片。
硅基光电子技术是一种颠覆性技术，为各种要求苛刻的应用提供光电子集成解决方案。将强大的硅集成电路制造技术应用于光电子器件的生产，能够获得更高性能的光路和系统，利用离散光子器件和/或III-V半导体技术可以提高集成度和成本效益。此外，相同的硅平台和制造流程可被用于在一块硅芯片上同时集成光、电子、和光电子部件。
Photonics Research 2017年第6卷第1期发表的一篇论文中（B.-M. Yu et al., Single-chip Si optical single-sideband modulator)，韩国延世大学的研究人员和德国高性能微电子创新研究所（IHP）成功开发工作频率为30 GHz的硅光单片集成单边带（OSSB）调制器，证明了光子和电子集成技术的可能性。传统光调制器产生双边带，而作为光纤无线通信技术关键组成部分的OSSB调制器只产生一个边带。在光纤无线通信技术中，高频电信号通过光纤在光域中传输，这样它们就可以避免由于许多要求苛刻的无线应用的损耗和干扰而衰减。为了实现OSSB调制器，需要在电学和光学领域进行信号处理。到目前为止，信号处理需要分别由电子和光子元件来完成，这使得OSSB调制器装置体积庞大且价格昂贵。延世大学和IHP的研究人员通过IHP的光电子BiCMOS制造技术在同一芯片上集成了高性能的单片硅基光电子器件和BiCMOS电路，将所有需要的电子和光学信号处理功能集中到一块硅芯片中。由此产生的OSSB调制器性能更好、尺寸更小，成本效益更高。总而言之，一块硅芯片成功地实现了常规情况下一整套设备才能实现的功能。
该论文的通讯作者——延世大学的Woo-Young Choi教授认为这项工作清楚地展示了硅基光电子和电子集成技术的潜力，许多激动人心的新应用要求将光子学和电子学功能同时集成在一块芯片上，而这项技术的出现无疑为这些应用的实现打开了一扇大门。