Ultimate Control in Semiconductor Lasers

Current applications for semiconductor lasers are wide ranging and pervade every aspect of life. Indeed, in the developed world, most people already own several lasers and gain the benefit of many more. With every new technology, this proliferation is set to continue. Most importantly, the laser enables the internet age since all data transmitted around the globe is carried as flashes of laser light. As a consequence most people in the developed world have come to depend on many lasers during a typical day. The reduction in their cost of ownership is therefore of critical importance to the extension of these benefits to the developing world and also bringing new benefits to us all.

The potential future applications of photonics are seemingly unlimited, with new technologies and applications continuing to emerge. The key advantage of a semiconductor laser is that if an application has sufficiently large volume, the cost of the semiconductor laser is very low. The DVD player is a good example -with the laser costing a few pence each. The semiconductor laser therefore enables new technologies, devices and processes to be commercialized. However, semiconductor lasers must be able to generate the required "flavour" of light; i.e. the correct wavelength, spectral width, power, polarization, beam shape, etc.

Some of the fundamental parameters of a semiconductor laser may be controlled by the design and choice of materials, e.g. wavelength, spectral purity (line-width). However, using current technologies the polarization and beam profile are generally fixed at manufacture and may only be subsequently altered by extrinsic optical components. This introduces additional cost (increasing the environmental impact) and reduces the overall efficiency and usefulness of the device. For future engineers and scientists it would be ideal if there were complete control of the output from a semiconductor laser, providing unlimited possibilities in terms of future applications.

The alteration of matter on the scale of the wavelength of light is known to allow the control of the optical properties of a material. Even the laser in something as simple as a mouse incorporates a number of such technologies. We will develop novel nano-scale semiconductor fabrication to modify light-matter interaction and engineer the control of the polarization and form of a laser beam. Our work will realise a volume manufacturable photonic crystal surface emitting laser (PCSEL) for the first time. The nano-scale photonic crystal is responsible for controlling the properties of the laser. It is simply a periodic pattern similar in size to the light itself, a natural example of this periodic patterning produces the blue colour in some butterfly wings, or the iridescence of opal. In our case, every detail of the photonic crystal will be modeled, understood and optimized to control the properties of the laser to meet a range of needs. Lasers will be designed to exhibit almost zero divergence and will also allow, for the first time, the electronic control of divergence and polarization and allow the direct creation of custom engineered beam profiles and patterns. The realization of high efficiency, area scalable high power lasers with ideal beam profiles will contribute to reduced energy consumption in the manufacture of laser devices, and in their cost of ownership. The technologies developed will allow the ultimate in design control of future optical sources, hopefully limiting laser applications only to the imagination.

Once successful, such devices will displace existing lasers in established commercial photonics and enable many more emerging application areas. This will be made possible by introducing both new functionality to laser devices and reducing the cost of existing products. We will develop this technology alongside physical understanding and device engineering, liaising closely with world-leaders in the volume manufacturer of such devices.

Semiconductor lasers are at the heart of many consumer electronics products, and drive the internet-age. They have clearly played a significant part in changing the way we communicate. A growing requirement for low cost (manufacture and ownership) lasers is therefore clear. This is further reinforced by recent assessments of the "carbon footprint" of various sectors which indicate that data handling for the internet is of greater environmental impact than aviation. In addition, in the coming decades semiconductor lasers are set to have significant future impact in our lives in imaging and sensing in healthcare, security and environmental monitoring. For example, in the near future, applications may include; imaging directly onto the retina, projecting a video image from your mobile phone, low energy laser projection TV, monitoring of health through breath monitoring, 3D structural and functional tissue imaging, therapy and surgery, in gas monitoring of emissions and real-time engine management, or in remotely detecting security threats. It is our vision that by developing the ultimate in control in the output characteristics a semiconductor laser diode, that the application areas are limited only by the imagination of scientists and engineers, providing significant knock-on societal impact. A combination of improved performance and a reduction in the cost of ownership with allow currently high end devices to become within the reach of the general population. These developments will both improve the quality of life for the user and reduce the economic and environmental impact of their use. Furthermore, device improvements and cost reduction will enable the spreading of currently 'developed world' technology to the developing nations, especially important in the fields of healthcare and improving quality of life.

The development of lasers with the ultimate in design control of the emitted light will enable a new range of future applications. This is clearly in line with the EPSRC plan to focus the optoelectronic devices and circuit theme towards future systems applications (photonics for future systems). A wide range of groups will benefit from this new improved technology, from the designer, manufacturer, installer through to the person on the street owning, gaining access to, or having the use of, high performance photonic technology.

In terms of manufacturing benefit, improved performance will enable competitive advantage and maintaining profitability against price erosion from the far east. The potentially low cost aspect to the lasers developed in this project will enable the manufacturer to reduce prices whilst maintaining profit margin, and therefore secure increased business. These two aspects of benefiting from technology innovation and improvement are particular important in the European business model where labour costs are higher than other competing countries.

The creation of new products and procedures can be expected to create economic impact through the generation of patent license agreements, the creation of spin-out companies, or inward investment and the creation of R&D laboratories in the UK. Our close relationship to our Technology Transfer Office will be fully exploited. Opportunities will be maximised through quarterly contact with our commercial partners to update them on progress, and highlight commercialisation opportunities. This process is discussed further in the "Pathways to Impact" document.

In addition to the training of scientific project members in areas such as photonic band-gap design, semiconductor fabrication technologies, etc., this project will provide a platform for the training of all team members in areas which will be transferable to other employment areas such as;
*Business needs of key players in laser manufacturing, and how this translates into engineering research
*Exposure to emerging areas of research in disparate fields
*IP assessment and protection