Setup and Characterization of an Optical Feedback Cavity System for Nanoparticle Detection

In the recent past, nanoparticles have gained an enormous interest in environmental science. They are abundant in the atmosphere and can get attracted to the lung and cause health issues as well as act as condensation nuclei and therefore effect the formation of clouds. These effects depend on particle composition as well as surface structure. In many applications, large particle size distributions are investigated and since surface structure and composition varies with particle size, size resolved measurements like in a single particle mass spectrometer are of desire. Currently, these instruments are only able to detect particles down to about 200nm. However, a large amount of particles in the atmosphere are smaller. In this contribution, we present a novel experimental setup based on an optical feedback enhanced cavity system which will allow us to detect scattered light of particles down to about 60nm. This tool will allow us to measure the size of the investigated particle, the position as well as the speed. Introducing such an optical setup in a single particle mass spectrometer or combining it with XPS measurements will allow us to perform size resolved measurements of particle composition and surface structure down to particle sizes of approximately 60nm which represents an enormous improvement in investigating the influence of atmospheric nanoparticles.