Research objectives and content
The aim of this project is the development of mid-lR lasers with wavelengths of 4.2 micrometers (an absorption line of CO2) or longer from narrow-gap III-V semiconductors. These lasers provide a large variety of potential applications for gas sensing. The development of the laser diodes will benefit from the very successful light emitting diode (LED) project of my host group. The novel type-ll strained layer superlattice structure of these . LED's will be used as the active layer of the lasers. Furthermore, waveguiding and carrier confinement has yet to be achieved for lasing action. The development of the waveguiding layers is a key part of this project. The complete development of the laser diodes involves issues as - High quality growth of the layers. - Device characterisation with variety of spectroscopic techniques. . - Device modelling, including co-operation with several research groups world-wide. - Device optimisation by feedback from experimental device characterisation and theoretical device modelling. Process for optimisation of the devices. As a result, we expect the demonstration of lasing beyond 4.2 micrometers at higher temperatures than previously achieved. The advantage of the use of the novel type-lI strained layer superlattices will be demonstrated. Our guiding aim is to produce room temperature laser diodes suited for commercial CO2 sensing applications.
Training content (objective, benefit and expected impact)
My training concerns all relevant processes of the laser diode development. This includes molecular beam epitaxy growth, clean room processing and experimental characterisation. In all of these fields I will have access to state- . of-the-art equipment - some world-wide unique. Together with my host group's extensive experience this provides an ideal base for an immense benefit of my training. The stimulating surrounding at Imperial College with its advanced postgraduate courses will further widen my horizon beyond this project.
Links with industry / industrial relevance (22)
The industrial market for small and cheap gas sensing devices for pollution monitoring is huge. Links with industry will be provided via the group's very successful LED programme. Research grants (sponsored partly by the UK government) exist with Edinburgh Sensors for the development of practical sources for IR gas sensing systems and with Omitech Ltd. for the usage of LED's in vehicle exhaust monitoring stations. Several small European . companies like 3 gas sensor manufacturers, 2 offshore safety monitoring equipment manufactures, as well as Royal . Dutch Shell and the US Air Pollution Monitoring Agency explicitly expressed their interest in the laser diodes subject to this proposal.