The ever-increasing growth in data traffic requires more powerful transmission networks.  To respond to such demand, a group of researchers led by Prof. Xiankai Sun and Prof. Hon Ki Tsang in the Department of Electronic Engineering, The Chinese University of Hong Kong (CUHK) has recently revealed a way to use light to convey large rates of data in advanced optical chips. Their findings and demonstrations shed new light on increasing the data capacity with low insertion loss and crosstalk. These research results have been recently published in the prestigious scientific journal Nature Communications.

The conventional optical communication is based on total internal reflection, creating a high-refractive-index channel, for the light wave to propagate. Bound states in the continuum (BICs) refer to a type of wave that can coexist with continuous waves without any radiation loss.  Applying BICs in photonic integrated circuits enables low-loss light guidance in low-refractive-index channels on high-refractive-index substrates, lowering the cost and the complexity of processing.  The research team applied them on an etchless lithium niobate integrated photonic platform and has successfully confined light without adopting the high-refractive-index channel.

Prof. Xiankai Sun said, “The BIC concept makes it unnecessary to invent new high-refractive-index polymers to form waveguide channels on the high-refractive-index substrate or etch the substrate in order to guide light in channels in the substrate.”

Optical interconnections with ultrahigh data capacity are needed in high-performance computers and data centres.  To further increase the data transmission capacity, optical multiplexing technologies are used to transmit multiple channels of data in parallel. By making use of carefully engineered high-order BICs on a planar lithium niobate substrate, the team demonstrated the viability of the BIC concept for use in high-capacity optical communication links by using different spatial modes for mode-division multiplexing.

Prof. Sun added, “With this new technology, we can obtain an aggregate data rate of 160 Gb/s per wavelength light carrier on the lithium niobate platform which, with the additional advantages of high thermal stability and high linearity, will bring optical communication to a new level.”

Department of Electronic Engineering, CUHK

The Department of Electronic Engineering was established in 1970 by the 2009 Nobel Laureate in Physics, Prof. Charles Kao. The department aims at educating students to enhance their potential to become leaders in electronic engineering and instill in them the desire to pursue knowledge and advance the state of the art in electronic engineering, which includes hardware, software, and design aspects of electronics as the core, ranging from materials, devices, circuits to systems and their applications. The department has 21 professors and teaching staff complemented by 56 research and technical support staff members, serving 227 undergraduate students, 128 research postgraduate students pursuing PhD and MPhil degrees, and 39 postgraduate students pursuing MSc degrees.

Professor Martin D.F. Wong, Dean of the Faculty of Engineering, has been elected Fellow of the  Hong Kong Academy of Engineering Sciences (HKAES) in December 2019.  The Induction Ceremony took place on 30 June 2020.

A world-renowned scholar and expert on electronic design automation (EDA), Prof. Wong has published over 450 refereed articles at top journals and conferences.  His research interests include EDA, combinatorial optimisation, graph algorithms, parallel processing, cloud computing and machine learning.  He is also a Fellow of the Association for Computing Machinery (ACM) and the Institute of Electrical and Electronic Engineers (IEEE) for his contributions to the algorithmic aspects of EDA, and has won a number of prestigious awards from ACM and IEEE.

The Hong Kong Academy of Engineering Sciences was founded in 1994. It is an organization of Hong Kong’s most eminent engineers of various disciplines who are recognized leaders of the profession with distinguished achievements in engineering sciences or applications.

Prof. Martin Wong elected HKAES Fellow (4th right, front) 

Prof. Ming Yu, Department of Electronic Engineering has been selected for the 2020 Microwave Application Award of the IEEE Microwave Theory and Techniques Society (MTT-S) for his contribution to the development of computer aided and robotic tuning for filters and multiplexers.  The award recognizes an individual or team of no more than five individuals for an outstanding application of microwave theory and techniques, which has been reduced to practice nominally 10 years before the award.

Filters and multiplexer are widely used in high frequency circuits in wireless communication systems. It is an important constituent of building reliable microwave communication network such as 5G build out and Satellites. Prof. Yu has a distinguished track record in the electronic engineering industry for decades before joining CUHK. He is well recognised for his work on developing the computer aided tuning (CAT) software for COM DEV in Canada in 1995, which was the first industry application of CAT.  He received the COM DEV CEO’s Achievement Award for the development of computer-aided tuning for microwave filters in 1995 and 2006 respectively, becoming the first person to receive the highest honor in COM DEV International Ltd twice. His pioneer works are widely followed worldwide in industries, specially in wireless applications. In 2003, he demonstrated the world’s first robotic filter/diplexer tuning system at an IEEE MTT-S conference workshop in Philadelphia, PA.

Prof. Yu received the Ph.D. degree in electrical engineering from the University of Victoria, Victoria, BC, Canada, in 1995. He joined COM DEV International, Cambridge, ON, Canada, as a Member of Technical Staff since 1993 and was involved in designing passive microwave/RF hardware for both space and ground-based applications.  He was a Principal Developer of a variety of COM DEV's core design and tuning software for microwave filters and multiplexers. He was a Manager of Filter/Multiplexer Technology (Space Group) and a Staff Scientist of Corporate Research and Development.  Until 2016, he was the Chief Scientist and the Director of Research and Development overseeing the development of company's research and development roadmap and next generation products and technologies, including high-frequency and high-power engineering, electromagnetic-based CAD and tuning for complex and large problems, and novel miniaturization techniques for microwave networks. Prof. Yu has also led the Advanced Technology Group, Cambridge, as the Chief Scientist and an Engineering Fellow. He was later promoted to Senior Honeywell Engineering Fellow, highest honor in a 140,000-employee organization.

Since joining CUHK in 2017, Prof. Yu has secured about $20M research funds, mainly from leading industry players. He has set up a joint Faculty lab named SpaceLab. He is focusing on developing high performance RF and microwave devices and systems for terrestrial and space communication systems. His team is working on Advanced electromagnetic CAD, synthesis, modeling and low-cost manufacturing technique for filters, multiplexers, antennas and other passive devices; applied machine learning for microwave engineering. He is also helping industry to solve many immediate issues such as IC designs and high-power problems.

Prof. Yu is an IEEE Fellow and a Fellow of the Canadian Academy of Engineering. He was an IEEE Distinguished Microwave Lecturer from 2010 to 2012. He is now a member of IEEE speaker's bureau. He served as an IEEE MTT society Filter Committee Chair (MTT-8) and Chair of MTT technical committee TPC-11. He was an Associate Editor of the IEEE Transactions on Microwave Theory and Techniques. Prof. Yu is the TPC Chair of 2020 Asia Pacific Microwave Conference in to be held in Hong Kong Science Park. He published over 30 patents. He has authored or co-authored over 150 publications and numerous proprietary reports.

The award will be conferred at the annual Society Awards Meeting for August 2020 at the International Microwave Symposium to be held in Los Angel, California.

More details of Prof. Yu’s work can be found at :  http://www.ee.cuhk.edu.hk/~mingyu/Research.html

A research team led by Prof. Wei Ren has adopted high-level quantum chemistry calculations to provide a definitive answer to the role of water vapour in some important atmospheric reactions. The new findings will enable a more accurate and reliable prediction of air pollution and atmospheric chemistry.

Volatile organic compounds (VOCs) will produce ozone and fine suspended particulates (PM2.5) under photochemical reactions. In recent years, people in Hong Kong may have experienced fewer ‘blue sky’ days. One of the major reasons is the increasing emission of VOCs from the surrounding areas. Methanol is one of the most significant VOCs in the atmosphere with a global emission of 2.4 million tons. The lifetime of methanol in the atmosphere is about 3 to 14 days.

Hydroxyl radical (OH), known as the ‘detergent’ of the atmosphere, is one of the most important species controlling the oxidizing capacity of the global atmosphere. It initiates most oxidation processes and removes the majority of gases emitted into the atmosphere including VOCs. Due to its significant environmental impact, scientists have been adopting numerous experimental and theoretical tools to understand some key oxidation reactions in the atmosphere. On this basis, reliable computational models can be constructed and used to predict air pollutions and atmospheric change.

It has long been hypothesized that water vapour, with a concentration of 3% in the atmosphere, may play a role in atmospheric reactions involving VOCs oxidations. However, no direct evidence is reported until recently. In 2017, a research group in Argentina experimentally observed that the reaction of methanol with OH could be accelerated by a factor of two in the presence of high relative humidity. Thus they concluded that the water molecules affect the atmospheric methanol reactions. However, another research group from the French National Centre for Scientific Research claimed no catalytic effect of water vapour in their similar experiment. Doubt is cast on the possible role of water vapour in this reaction system.

To clarify the role of water vapour in atmospheric methanol oxidation reactions, Prof. Ren’s team at CUHK worked with the University of Minnesota’s team adopting a high-accuracy quantum chemistry method and variational transition state theory to study the particular reaction involving methanol, hydroxyl and water vapour. With a thorough consideration of the high- and low-frequency anharmonicity, variational effect along the reaction path, and the quantum tunneling effect, the termolecular rate coefficients at 200 to 400 K were calculated. The theoretical calculation confirms that the catalytic effect of water vapour on the methanol and hydroxyl reaction is negligible in the atmosphere. The research work has been reported in the renowned scientific journal, Angewandte Chemie-International Edition and was highlighted as the Very Important Paper (VIP). (https://doi.org/10.1002/anie.202001065) 

Professor Ren said, “this research unveils a novel method for predicting atmospheric reactions.  With the new dimension provided for the study of atmospheric reactions, we hope that in the future there will be a more accurate and faster application on monitoring air pollution in addition to the ultrasensitive trace gas sensors, leading to a higher quality alert system, and even better precautionary measures by the relevant corporations and authorities.”

Additionally, Prof. Ren’s team explored the reaction rate coefficients of cyclopentane reaction with hydroxyl, which plays a significant role in fuel combustion and atmospheric degradation. This work exemplifies a valuable practice of extending the state of the art of treating anharmonicities in chemical reaction systems. This work has been recently published as Advance Article in Chemical Science-The Royal Society of Chemistry  (https://doi.org/10.1039/C9SC05632G).