"The overall aim of the work described in this proposal is to create a long-term strategic partnership between Sheffield University, Radboud University, M-Squared Lasers and Sensor Sense in order to develop a new generation of instrumentation for ultra-high sensitivity trace gas detection based on novel, mid infrared quantum cascade lasers emitting in the 3-4 micron wavelength range. The 3-4 micron wavelength range is of key technological importance for a wide range of applications. Many important hydrocarbon species, for example ethane, methane, acetone, formaldehyde and butane and other molecules such as hydrogen halides have their strongest absorption features in this region, and detection sensitivities are therefore maximised. This leads to many potential applications in areas such as clinical diagnostics (breath analysis), process monitoring, control of outdoor and indoor pollution, remote detection of oil and gas deposits and explosives and concealed weapons detection. Consequently, there is very strong motivation for the development of compact, high performance sensing systems in this wavelength range, which will provide major opportunities for wealth creation and enhanced quality of life.This highly interdisciplinary project brings together leading groups with strongly complementary and synergistic expertise in semiconductor physics, infrared lasers, optoelectronics technology, molecular absorption spectroscopy and advanced gas detection technologies. The consortium is thus very strongly placed to make major contributions to EU competitiveness in this increasingly important technological area."