Light People: Prof. Daoxin Dai, Dr. Patrick Lo, and Prof. Yikai Su—innovators in silicon photonics

Wan and Guo Light: Science & Applications (2024)13:287 https://doi.org/10.1038/s41377-024-01650-8 LIGHT PEOPLE Official journal of the CIOMP 2047-7538 www.nature.com/lsa Open Access Light People: Prof. Daoxin Dai, Dr. Patrick Lo, and Prof. Yikai Su—innovators in silicon photonics Yating Wan 1✉ and Chenzi Guo2 ✉ 1234567890():,; 1234567890():,; 1234567890():,; 1234567890():,; Editorial In this edition of Light People, we are excited to feature Prof. Daoxin Dai (Zhejiang University), Prof. Yikai Su (Shanghai Jiao Tong University), and Dr. Patrick Lo (Advanced Micro Foundry Pte Ltd, Singapore), three prominent researchers shaping the future of silicon photonics. Their collaborative work addresses critical issues in silicon photonics, including reducing propagation losses, enlarging the functionalities and enhancing building blocks, integrating efficient laser sources, expanding applications, and pushing the boundaries of optical and electronic integration. Through this interview, we delve into their academic journeys, challenges, and future visions, offering insights into the ongoing evolution of silicon photonics and its potential to transform industries. For a deeper exploration of their experiences and advice, the full interview is available in the Supplementary material. Can you briefly describe your current work in silicon photonics, what initially attracted you to this field, and how has your focus shifted over time? Yikai: Our group, the Optical Transmission and Integrated Photonics Group, initiated research in silicon photonics in 2006, focusing primarily on silicon devices. I was attracted to this field due to silicon’s high refractive index, which facilitates high-density integration and its compatibility with existing CMOS fabrication processes. This compatibility simplifies the fabrication process when compared to materials like III–V semiconductors. Recently, our focus has broadened to include other promising materials, such as the heterogeneous integration of silicon nitride with lithium niobate, which offers unique properties that complement silicon. Daoxin: My team is dedicated to developing highperformance silicon photonic devices and aiming to create large-scale silicon photonic circuits for applications like optical interconnects and optical computing. My interest began during my Ph.D. with my work on planar lightwave circuits using silica on silicon, which has weak Correspondence: Yating Wan () or Chenzi Guo () 1 Electrical and Computer Engineering, the Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology, 23955-6900 Thuwal, Saudi Arabia 2 Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, China optical confinement and limits integration density. Recognizing silicon’s potential for high-density integration owing to its strong optical confinement, my research has evolved from focusing on compact functional devices to pursuing large-scale integration of various elements on a single chip. Patrick: I initially focused on hardcore CMOS technologies during my Ph.D. and initial industry work, namely on CMOS process and transistor devices research. After I moved to Singapore in 2004, I began to seek alternative semiconductor research areas, including nanodevices, shortly after in 2006, I started exploring silicon photonics, drawn by its potential in areas beyond traditional scaling limits, a concept often referred to as ‘More than Moore”, fancied just by the notion from electrons to photons and electrons. At the Institute of Microelectronics (IME) at that time, we pioneered the development of capacitor-based modulators shortly after Intel. From the very beginning, in order to be true value-adders and be differentiative from either purely academic or pure industrial research, we were very clear that our work needed to center around creating technology platforms that were transitionable to industry-nature product platforms, which subsequently catalyzed the establishment of dedicated foundries. Over time, my focus has been shifting back and forth between the essential device physics and end application, and product exploration of such © The Author(s) 2024 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. Wan and Guo Light: Science & Applications (2024)13:287 attitudes has been instrumental in always guiding us in continuously commercializing our findings. With our industrial partners, the team successfully launched the first 100G coherent products and, subsequently, the 400G products. This successful transition from lab to market commercialization over the last decade has been immensely rewarding, for one, providing great confidence to both industry and academic circles. For example, you might have appreciated the trend of research funding that has been hugely poured in from private industry in addition to the typical source from the government, from a few regional activities to be very global. Given the rapid evolution of silicon photonics and the increased services offered by major fabs, what are the major challenges facing silicon photonics today? Daoxin: While silicon photonics has become mainstream, we still face significant challenges in achieving high-performance devices and high-yield, large-scale circuits that meet the demands of real-world applications. For instance, a typical single-mode silicon waveguide with a cross-section of 450 nm × 220 nm suffers from a propagation loss of 1–2 dB/cm, which is substantial over longer distances. Looking ahead, we need to address three areas: exploring materials beyond silicon to overcome its limitations, moving beyond the single-mode regime to reduce propagation loss and phase errors, and broadening the applications of silicon photonics with devices for visible and mid-infrared light, which holds both opportunities and challenges. Patrick: From an industry perspective, expanding the applications of silicon photonics involves incorporating various materials to support different wavelengths, functionalities, and performance. Frankly, Silicon is not the best material for optics in many accounts, but it’s the best (...truncated)