£470k EPSRC funding for Novel photonic sampling

UCL Photonics Group Research expected to impact radar systems, medical imaging and wireless communications

Congratulations to Dr Chin-Pang Liu whose research project titled 'Photonic Sampling using an Agile Optical Comb Generator' has just received over £470,000 funding.

Our society is highly connected through various digital services. However, much of the information we exchange and process is of an analogue nature in its origin. Analogue-to-digital conversion is thus already an integral part of our modern digital society. Digital signal processing is a powerful technique for storing, analysing and manipulating digital signals. Ultimately, the quality of the signal to be processed is determined by the performance of the analogue-to-digital converter (ADC) which is used to sample the original analogue signal in the first place and produce a digital representation of it. Electronic ADCs are embedded ubiquitously in numerous everyday items, such as mobile phones, digital cameras and computer mice. As the speed of electronic ADCs continues to increase, more and more sophisticated applications including medical imaging, 60GHz wireless communications and cognitive radar can benefit from the use of ADCs and digital signal processing, which are all important to our society and economy.

"In Medical Resonance Imaging (MRI) for example, a large amount of data is generated which need to be moved out of the scanner, digitised and then processed. Because of the extremely strong magnetic field around the scanner, reducing the number of metal cables is important. The proposed photonic sampling allows the sampling of the signals as close to the source as possible and uses optical fibre, which is not affected by magnetic field, to transport the sampled signal away from the scanner. This has the potential of enhancing the performance as well as reducing the cost of MRI scanners, thus improving the well-being of the citizens."


Photonics has been used to increase the performance of electronic ADCs since the 1970s, forming what is now generally termed the photonic ADC. Most photonic ADCs with sampling rates as high as 1 THz (or 1,000,000,000,000 Hz) have employed mode-locked lasers, as they can produce very high power optical pulses with very short pulse widths and low jitters, both in the fs region. Such optical pulses are ideal for sampling microwave and millimetre-wave signals in conjunction with a Mach Zehnder modulator (MZM) or a photo-conductive switch as reported in previous work from the Photonics Group at UCL.

The overall project objective is to investigate experimentally a novel, low-jitter sampling technique using a frequency agile optical comb generator for microwave and millimetre-wave signals. Compared to the traditional approach using bulky and expensive mode-locked lasers with inflexible sampling frequencies, Dr Liu's proposed technique based on an optical comb generator allows highly adjustable sampling frequencies to suit the different centre frequencies and bandwidths of the input signals. These attributes are important for the next 10 to 50 years as the lower parts of the radio spectrum become congested by increasing numbers of higher throughput wireless services, and society and policy makers in the UK and elsewhere are forced to use frequency bands at 60 GHz or higher. Dr Liu expects his technique to find applications and generate impacts in a wide range of areas, including radar systems, medical imaging and wireless-over-fibre communications.

Dr Liu will be recruiting an RA to work alongside him and the co-investigator Professor Alwyn Seeds to carry out the research. This will be advertised on our vacancies page (LINK) in the next few weeks. The research will be carried out in participation with Thales UK, who manufacture radar and satellite systems and employ around 7500 staff in the UK.

About the Principal Investigator: Dr Chin-Pang Liu

Dr Chin-Pang Liu has over 18 years of experience of semiconductor photonic devices, microwave and millimetre-wave over fibre systems. Dr. Chin-Pang Liu received the First-Class B.Eng. (Hons.) Degree and the Ph.D. Degree in electronic and electrical engineering from University College London (UCL), London, U.K., in 1994 and 2000, respectively. His Ph.D. research topic was optoelectronic mixing in heterojunction bipolar transistors. He worked for JVC in Hong Kong from 1994 to 1995 as project coordinator. He was a Research Fellow from 2000 to 2009 and is now a Lecturer in Photonics at UCL.

During his undergraduate and postgraduate years, he won an IEE Institution Prize in 1994, an Overseas Research Students Award in 1995 and the Best Student Presentation (Devices, Components and Techniques) at the 1999 IEEE International Topical Meeting on Microwave Photonics in Melbourne, Australia.

Dr. Liu served on the technical program committees for the 2008 International Topical Meeting on Microwave Photonics and the Annual Meetings of the IEEE Photonics Society in 2009 and 2010. He is also a regular reviewer for the IET Optoelectronics, the IEEE Photonics Technology Letters and the Journal of Lightwave Technology.

About the Co-Investigator: Professor Alwyn J Seeds

Professor Alwyn J. Seeds has extensive experience of semiconductor photonic devices, high capacity optical communication, wireless over fibre systems as well as THz signal generation, transmission and detection. He invented the optical injection phase lock loop (OIPLL) and developed the first nonline narrowed semiconductor laser heterodyne optical phase lock loops (OPLL) as well as demonstrating the first optical comb locked OPLLs.

Professor Seeds holds the B.Sc. degree in Electronics, the Ph.D. degree in Electronic Engineering and the D.Sc. (Eng.) degree, all from the University of London. From 1980 to 1983 he was a Staff Member at Lincoln Laboratory, Massachusetts Institute of Technology. He was appointed Lecturer in Telecommunications at Queen Mary University of London in 1983. In 1986 he moved to UCL where he is currently Professor of Opto-electronics and Head of the Photonics Group. Professor Seeds is Chairman of the IEE Photonics Professional Network, a Past-Chair of the IEEE International Topical Meeting on Microwave Photonics, Steering Committee and has served as the Conference Chairman or Technical Programme Committee Chairman for many international conferences. He is a co-founder of ZinWave Inc., a wireless technology company. He was elected an IEEE Fellow in 1997 for his contributions to the development of microwave photonic devices and systems and a Fellow of the Royal Academy of Engineering in 2003.

Professor Seeds is author of over 250 papers on microwave and opto-electronic devices and their systems applications and presenter of the video "Microwave Opto-electronics" in the IEEE Emerging Technologies series.