New lasers detect harmful pollutants
It is estimated that the Earth's average temperature has risen over the past several decades. This change is not part of the natural cycle of warming and cooling of the global climate. Rather it is due to emissions of carbon dioxide, methane and other greenhouse gases from man-made sources. The emissions are primarily driven by the combustion of fossil fuels in power plants and automobiles. Man must be able to measure these emissions in order to make the changes necessary to reverse global warming. The two most important greenhouse gases, carbon dioxide and methane, both absorb light in mid-infrared region of the spectrum. This corresponds to wavelengths between 3 and 4 microns. One of the biggest challenges in constructing robust monitoring equipment is the issue of overheating. Ideally, the equipment should be able to operate at room temperature. Research supported by the BRITE/EURAM 3 Programme aspired to meet this challenge. The goal was to develop light-emitting diodes (LEDs) and lasers based on promising Group III Antimonide semiconductor technology. Prototypes were created with metal organic vapor phase epitaxy (MOVPE), which had previously never been done. Significant progress was made in refining the process to reduce the level of background impurities. The project was successful in creating LEDs measuring in the desired frequency range while operating at room temperature. Further work on the lasers is necessary, where operating temperatures reached 135 degrees Celsius. The results were disseminated to the academic and industrial communities through publications and conferences. Members of the research consortium have launched new products and services related to both the sensors and the improved MOVPE technology. The main application of these cutting edge sensors is in the detection of greenhouse gases, such as carbon dioxide and methane. Networks of sensors can monitor ambient concentrations while individual sensors can measure emissions from a single source (e.g. an automobile). There is also potential for thermo-photovoltaic devices for converting infrared radiation and heat into electricity.
