Terahertz Micromachined Resonator Superstructures

This application has three distinct but interrelated research areas. The first is a method of designing microwave circuits using inter-coupled resonators. The method is extremely general, and can be used over a wide frequency range with many different technologies used in microwave circuits. The second area is using micromachined terahertz devices to exemplify the new deign techniques at a particular frequency and for a particular application. Micromachining has to be used to make accurate dimensioned waveguides with accuracies down to microns. The third area is the improvement in the micromachining process for the terahertz application.Inter-coupled resonators have been used for many years to make microwave filters. For more complex passpand responses with transmission zeros or dual bands, the inter-coupling becomes much more complex. This proposal takes this concept a stage further and proposes that whole passive systems can be made using coupled resonators or resonator superstructures. To exemplify this the authors have already demonstrated power splitters and a diplexers based on these concepts, and the proposed work is to look at antenna feed networks, Butler matrices and filter banks. The techniques can provide the design of microwave circuits at any centre frequency and will be useful in many areas. Technology is now allowing systems to be constructed at much higher frequencies; mobile communications at around 2 GHz is now commonplace, but car radar systems at 77 GHz have only just developed in the last few years, and now applications are beginning to emerge at above 100 GHz in the submillimetre wave region. Applications to 1 terahertz and above are seen as extremely important for future systems. One of the lowest loss waveguide structures is the rectangular waveguide, and this work will look at micromachined waveguide. The circuits are made by stacking layers of metalised silicon or thick resists. Two of the layers act as the top and bottom of the guide and the interleaving layer (or layers) forms the walls of the hollow rectangular tube. For 300GHz these waveguide are about 800 by 400 microns and micromachining is therefore required to make them accurately at this size. At Birmingham a reliable, accurate techniques for bonding the layers has been developed. Structures such as filters, power splitters, diplexers and triplexers will be demonstrated. The resonator superstructures will be also configured in waveguide resonators to produce submillimetre wave antenna feed networks, Butler matrices and filter banks.Finally work will be done to improve the micromachining process. This includes being able to selectively pattern the top and vertical edges of the gold coating. This will enable transitions to other transmissions structures such as coplanar waveguides as well as the ability to improve the bonding between layers. In addition work will proceed on the development of a new dielectric waveguide structure, initially looking at the embedding of quartz nano particles in the resist SU8. Providing a low loss waveguide structure will give the microwave designer another tool for circuit construction.

Terahertz offers applications such as astronomy, gas spectroscopy including pollution monitoring, short range secure terrestrial communications, secure (narrow beam) satellite communications, modelling radar cross sections of large objects, security imaging and time-domain spectroscopy including medical sample imaging. We believe the micromachined waveguide technology offers a new inexpensive alternative to conventional waveguide or quasi-optic approach enabling the integration of complex passive systems. The use of waveguide passive systems at lower frequencies is ubiquitous and our technology allows these systems to be developed up to a few terahertz. The potential impact of this work is therefore considerable. We also believe the second strand of the work, the resonator superstructures, is also of considerable importance as its parallel with meta-materials demonstrates. Microwave meta-materials are a huge research area and considerable advances have been made. Here our meta-material is designable for specific functionality opening up doors for complex integrated passive systems. This is a new area of research, which holds promise for systems anywhere in the microwave spectrum and could have considerable impact in the future. The training of people is implicit in this project, and the impact of this training will continue for many years to come. Various training activities are offered to all workers on this project. For this work to have direct economic impact further effort will be required, this may not be further scientific studies but may be commercial development. This commercial development would be considerable, but this is common to all new technologies. The first steps will be to protect IP and set up partnerships. Alta Innovations have been set up by the University to exploit potential commercial situations, to protect IPR and to negotiate agreements. In addition, the proposers have considerable experience and expertise in the area of technology transfer, negotiation, know-how and patents, having been personally involved in commercial start-up companies. The EDT group has been awarded two world patents in collaboration with industry on their previous work. The School has a strong awareness of the importance of entrepreneurial activities at the academic-industry interface. Birmingham University has a close relationship with our regional development agency, Advantage West Midlands. In addition there is a Business Development Manager assigned to the School who can be tasked to develop routes for exploitation of the research work. We also have worked with industry via the Knowledge Transfer partnership (KTP) and have found this an excellent route to exploitation and technology transfer One of the remits of the advisory committee is to help with both dissemination and exploitation. The committee has been chosen to have particular interest and expertise in the research areas in the proposal, and the members are ideally placed to either suggest exploitation in their own companies, or advise on other industrial routes. Of course one reason for the inclusion of the collaborators is the development of products and they are ideally placed. The potential for wealth creation is considerable for terahertz technology. Despite a number of years of effort the technology is still in its infancy and has huge potential for growth as the science advances. This work is part of this science.