Gallium nitride enabled hybrid and flexible photonics

Compound semiconductors lie at the heart of modern-day information and communications technologies, and of these none is currently more important than gallium nitride and its associated family of alloys. This material system allows the production of sophisticated optical devices (lasers, light-emitting diodes, photodiodes) covering the ultraviolet and visible spectrum for displays, optical data storage and photovoltaics; it enables the development of advanced microwave electronic devices (transistors) for high temperature, high power and high frequency operation. Most of the work currently undertaken with gallium nitride focuses on the basic material itself and the devices that can be made directly from it. Here, in a visionary programme interfacing to a wide range of other materials and disciplines, we seek to explore the unique potential of gallium nitride for 'hybrid and flexible photonics'. These two interrelated themes involve the integration of nitride semiconductor micro/nanostructures and devices with compatible hard and soft materials, which we take to include single crystal diamond, nanocomposites, polymer overlayers and substrates, printable electronics, organic resists, biopolymers, and metal/plasmonic structures. Imagine, for example, hybrid waveguide devices made from gallium nitride and diamond. These could generate and manipulate single photons of light, towards computation and communications systems exploiting the full potential of quantum mechanics, or could enable lasers to be made from diamond via the so-called stimulated Raman process. Imagine, furthermore, the transfer of gallium nitride devices onto flexible substrates and their control via printable electronics. This could facilitate large area micro-displays, and a wide range of instrumentation and communications systems. Imagine the wavelength conversion of gallium nitride emission via nanocomposites and metal-based plasmonic effects, as the basis of multi-gigahertz visible light communications systems. Imagine a range of nanophotonic sources capable of stuying fundamental energy transfer processes on a nanoscale and of performing ultra-high resolution photolithography and direct write patterning. All of these capabilities and more can be forseen by the development of hybrid technologies based on gallium nitride. They present tremendous opportunities for UK leadership in fields of science and technology as diverse as nanoscience, lasers and nonlinear optics, quantum information, bioscience and visible light communications.

Our programme concerns novel ways of generating light in solid-state systems and using it for communications, sensing and measurement. It engages with a number of breaking research areas of national and international importance, including Visible Light Communications, Advanced Photonic Instrumentation, Flexible Photonics, Diamond Photonics, and Integrated Quantum Photonics. We bring a common underpinning vision to these areas, in the shape of the potential of gallium nitride semiconductor materials science and device technology - the basis of today's blue, green and white light emitting diodes and Blu-Ray optical data storage - to help to define their coverage and impact. Our proposal is timely, in that the above themes have yet to be fully defined and scoped out as academic disciplines; the overall responsibility we undertake in the programme is to communicate our vision as widely as possible and work with a broad range of academic colleagues, professional bodies, industry and others, to promote these themes, help them to emerge, and ensure they contribute to UK leadership on the international stage. Furthermore, we are committed to systems and instrumentation demonstrations as the key motivation and target of our underpinning materials and devices work, ensuring that we have end-users and commercial exploitation in mind from the very beginnings of the programme. The above themes fit within a broader societal context in important areas including (i) Solid State Lighting, (ii) Displays, (iii) Secure and Universal Communications, (iv) Energy Efficient 'Green Photonics' Systems, and (v) Biomedicine. Thus solid-state lighting, poised to replace inefficient and short-lifetime incandescent and fluorescent lamps, can also be modulated at high data rates to provide secure and scalable optical communications capability in buildings, rooms, offices, laboratories and operating theatres, and in smart and autonomous systems. Display technologies can be envisaged with a combined communications function, so that mobile phones or personal digital assistants, for example, can act simultaneously as 'pico-projectors' of image data and personal optical communicators. These display technologies are evolving from all-inorganic to hybrid organic-inorganic or all-organic, and thus beginning to absorb the concepts and potentialities of flexible ('bendy') photonics. In several of these areas, novel communications concepts based on the properties of quantum mechanics are beginning to be appreciated in not just an esoteric but in a practical sense; the materials and systems we are considering are poised to help make these fundamental conceptions into practical systems concepts. Thus the personal and secure optical communicator of tomorrow (see above) might well, for example, use quantum encoding and be based on gallium nitride or diamond components. Photonic Instrumentation already makes considerable contributions in Biomedicine, from research to hospitals and clinics. The device technologies we envisage offer exciting prospects for new forms of microscopy, for neuroscience, for retinal and neural prosthesis, and for miniaturised diagnostic tools such a laboratory-on-a-chip. The developments above offer new opportunities to UK industry, in particular in the development of commercial optical systems modules, instruments, communications networks and infrastructure, and in associated software and control electronics. We will work with our wide range of company contacts and engagement programmes and mechanisms to ensure that industry is fully aware of the technical advances as they occur. Our programme is multi-disciplinary in nature and very hands-on and visual. We have found that this acts as an exciting draw to young people in pursuing careers in science, and we will continue to engage in this via science fairs, the Glasgow Science Centre, supporting school visits and talks, and in undergraduate projects and preparation for post-graduate work.