Interference spectroscopy with advanced comb sources

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Optical frequency combs are lasers that produce very short and stable light pulses. By providing a precise and simple link between optical and electrically measurable frequencies they ignited in 2000 a revolution in frequency metrology, the science of measuring oscillations and time. Time keeping is important because most measurement units are directly linked to time, as this is the physical quantity that we humans can measure most precisely. Hence, when you buy a volume of gas for your car or when you pay your utility bill, you rely on the international time standard maintained by national laboratories. More direct applications of a precise time standard include geo-localization using GPS-like systems and synchronizing all financial transactions on a global scale. Frequency combs are without a doubt the most precise optical sources ever produced and they accordingly promise revolutions in several other domains. The first and foremost is probably in optical spectroscopy, the science of determining the chemical composition of gasses, liquids and solids by measuring the interaction of light at different wavelengths (different “colors”) with matter. When you drink milk, its purity has been assessed using a spectrometer and when you check the weather forecasts to plan a long weekend, you are effectively making use of several spectrometers on satellites scrutinizing the atmosphere. Combs have a lot of potential to improve spectroscopy significantly but several shortcomings currently prevent a large-scale adoption of this new tool. The first factor is that they are complex and delicate sources requiring highly qualified researchers to maintain and operate. Second, they do not natively produce the right “color” to interrogate matter. They are currently in the near-infrared (wavelengths between 1 and 3µm) while spectroscopic sounding works better in the mid- and far-infrared (from 3 to 5µm and from 8 to 12µm). The research program proposed in this application will address these issues and contribute making compact and robust comb spectrometers in the mid-infrared a reality. An innovative chip laser platform will be used. This platform will allow putting several lasers on a single chip, such that the spectrometer will be small and inherently rugged because all needed optical functions will ultimately be put in a single piece of glass. Canada has a strong industrial base in optical spectroscopy, with companies in several provinces selling instruments worldwide to different market segments: from process automation for quality control in food and pharmaceutical production lines to remote sensing for security, meteorological and environmental monitoring. Faster and more sensitive spectrometers will thus not only contribute to better and safer products and to improved weather predictions or air quality measurements, but will also directly support a traditional strength of Canada’s high-tech economy.