Single-Cavity Dual-Comb Laser

Absorption spectroscopy enables the non-destructive determination of gas composition or the detection of molecules. For this purpose, one exposes the sample to broadband light and observes which colors of the incident light are absorbed. This specific absorption fingerprint enables us to draw conclusions about the gases present or their molecular structure.
The methodology described above has long been established in many scientific disciplines and works very well in laboratory operations in situations when a low resolution is sufficient. With complex gas mixtures, e.g., consisting of many different gasses, in addition to trace gases in small concentrations, this approach reaches its limits due to low color discrimination (resolution). Besides, conventional devices are relatively complex and bulky.
The invention of the optical frequency comb made it possible to increase the resolution of spectroscopic measurements drastically.
However, measuring devices based on this new technology have become more complex and either require sophisticated control loops to stabilize the light generated or continue to incorporate a bulky spectrometer.
In this project, we are researching a new approach in which two optical frequency combs are generated in one laser. These two frequency combs are stable relative to each other since they come from the same source. If you now use both frequency combs to generate a difference signal, this signal is stable enough for absorption spectroscopy applications even without control loops. Another advantage of this detection method known as "dual-comb" spectroscopy is that the required signal is measured with a simple light sensor. A bulky detector is no longer necessary to determine the composition of complex gases in high resolution.
With this project, we lay the foundations for simple high-resolution spectroscopy and investigate the potential of the new spectrometer method in the open field outside of a dedicated laboratory environment. Possible areas of application for this spectrometer are e.g., the measurement of greenhouse gases in the atmosphere or the monitoring of contamination in industrial production processes.