I played a leading role in the development of millimetre-wave monolithic integrated circuit technology, creating millimetre-wave transmitter integrated circuits in the early 1980s. These are now to be found in the IEEE Microwave Theory and Techniques Society Historical Collection.

I established the research area of Microwave Photonics with work on the use of optical signals to control microwave devices, work on optical beam forming in phased array systems and the development of techniques for the distribution of microwave signals, including wireless signals, over optical fibre. The latter work has given rise to an industry with annual turn-over of > $1 bn in which Zinwave, co-founded with colleagues from Cambridge University, plays a significant part. The field now has several international conferences devoted to it and hundreds of researchers working in it worldwide. My contribution has been recognised by numerous invitations to chair conferences, edit special issues, write review papers and present plenary talks on Microwave Photonics at leading international conferences. An invited review of the field, which I wrote with Keith Williams of NRL for the Journal of Lightwave Technology in 2006, has now been cited over 800 times, a high count for a systems paper. 

I also have played a leading role in coherent frequency synthesis techniques for optical communications, including the first heterodyne optical phase-lock loop to use non line-narrowed semiconductor lasers and the first demonstration of the use of such loops with optical comb generators for frequency agile Dense Wavelength Division Multiplex (DWDM). This work was developed to produce highly sensitive, interference rejecting, optical receivers for special applications. These concepts have become enablers for the future, very high spectral efficiency, optical communications systems required for the future growth of the internet.

I have developed photonic integration solutions for key sub-systems using hybrid and monolithic techniques. I have also been closely involved in the creation of the first practical semiconductor lasers on silicon substrates, work that has been extensively cited.

Current Personal Research Interests

Microwave photonic systems; photonic integration on silicon substrates; THz photonic devices and systems; systems photonics; advanced wireless systems, including location and other functions; coherent optical communications; broadband wireless over fibre access systems;  high spectral efficiency dense wavelength division multiplex (DWDM) systems; wavelength converters; novel applications of liquid crystal devices, including for microwave and THz beam-forming; fast opto-electronic devices; tuneable semiconductor lasers; optical control of microwave devices; mode-locked lasers; optical phase lock loops ; all-optical networks; optical signal processing; optical sampling; application of optical techniques in microwave systems.