Prof. Michael Rung-Tsong LYU, Chairman of Department of Computer Science and Engineering has received the second-class award in Natural Sciences from the Ministry of Education (MoE).  His project is titled “Reliability Prediction and Evaluation towards Software Services”.

In the era of big data, the rapid increase in data traffic has aroused urgent demands for high-speed optical transmission. Ms. Gao Yun, a PhD student under the supervision of Professor Shu Ching-tat Chester at the Department of Electronic Engineering has published a paper in Optica recently, titled “High-speed Van der Waals heterostructure tunnelling photodiodes integrated on silicon nitride waveguides”. The research team has designed, fabricated, and characterised a new family of integrated waveguide photodetectors that promises exceptional benefits for applications in data centre interconnects and supercomputers. Also authors of the paper are Professor Tsang Hon-ki and Mr. Zhou Guodong from the same Department.

In recent years, optical interconnects have been proposed to alleviate the thermal bottleneck of the clock frequency in conventional electrical interconnects in CMOS (Complementary Metal-Oxide-Semiconductor) integrated circuits, to provide new levels of computational capability. At the receiver side of optical communication systems, photodetectors are used to convert optical signals back into electrical signals for further processing. Graphene photodetectors have previously demonstrated ultrafast response and broadband operation. However, due to the absence of an electrical bandgap in graphene, the photodetectors usually suffer from a huge dark current under a direct current bias. The dark current refers to the unwanted excess leakage current that occurs in the absence of light. It gives rise to detrimental noise in an optical receiver circuit.

To minimise the dark current of graphene photodetectors, the research team has demonstrated van der Waals heterostructure tunnelling photodiodes integrated on silicon nitride (Si3N4) waveguides. At the telecom wavelengths, a high on/off current ratio (over 10,000), a responsivity of 0.24 A/W, and a large bandwidth (56 GHz) have been experimentally achieved. The on/off current ratio has three orders of improvement when compared with previous graphene photodetectors. Si3N4 is more suitable for CMOS-compatible backend processing than silicon. The lower relative permittivity of Si3N4 also benefits a smaller device capacitance, which makes Si3N4 a better material underneath a high-speed device. This work provides a viable route towards high-bandwidth and high-sensitivity integrated photodetectors for data centre interconnects and supercomputers.

Ms. Gao Yun also received the prestigious “OSA/Corning Women in Optical Communications Scholarships” at the Optical Fiber Communication Conference and Exhibition (OFC) in San Diego, California, in March 2019 based on related research in graphene-based high-speed waveguide photodetector
 

This article was originally published on CUHK Communications and Public Relations Office website and edited by the Faculty of Engineering.

Twenty-one student teams from CUHK received awards at the Hong Kong University Student Innovation and Entrepreneurship Competition 2019, held on 25 and 26 May, eighteen of which was formed by students of the Faculty of Engineering. 

The University, with the largest number of awards among tertiary institutions in Hong Kong, has also received the Outstanding Institution Award and completed a sweep of all ten Mathematics and Physics / Mechanics and Control Systems awards under the Innovation category, which exemplified CUHK’s research and innovation excellence in these areas.

Innovation First-class Award: Multi-modality Digital Holography-based Two-photon Excitation Microscope

Ren Mindan and his team members, who are PhD students from the Department of Mechanical and Automation Engineering, won the first-class award with “Multi-modality Digital Holography-based Two-photon Excitation Microscope”. The system combines a powerful Digital Micromirror Device (DMD) random-access scanner with high-speed resonant galvo-scanners to realise many new functionalities that no current commercial solutions can provide, especially the optical imaging functions such as video-rate fluorescent imaging with simultaneous multi-point optical stimulation, ultrafast axial scanning, multi-plane imaging, and curved plane imaging.

Ren Mindan said they developed the mechanical units and operating software in a year and a half, under the supervision of Prof. Shih-Chi Chen, Associate Professor from the Department of Mechanical and Automation Engineering. The team is now working with the Hong Kong Eye Hospital, using this new invention to find out the molecular mechanisms of optic nerve diseases and degeneration.

The Hong Kong University Student Innovation and Entrepreneurship Competition 2019 was organised by the Hong Kong New Generation Cultural Association.  A total of 676 students from 16 local tertiary institutions submitted 203 projects for the two categories of the competition, namely “Innovation” and “Entrepreneurship”.  Winning teams will represent Hong Kong at the biennial “Challenge Cup” National College Students’ Extracurricular Academic Science and Technology Contest, the China College Students’ “Internet Plus” Innovation and Entrepreneurship Competition and the Beijing-Hong Kong Youth Innovation and Entrepreneurship Cup.

The following is the list of CUHK awarded projects:

This article was originally published on CUHK Communications and Public Relations Office website and edited by the Faculty of Engineering.