Development of an optical particle number sensor based on continuous wave laser-induced incandescence

Abstract

In this work, the development of a new particle counting sensor based on continuous-wave laser-induced incandescence is described. We demonstrate the sensor, which makes use of a focussed laser beam emitted by a compact laser diode, as an alternative device to established laboratory techniques to count soot particles. Simulations help understanding the cause–effect relationships based on known theory with the implementation of specific laser beam characteristics that influence the absorption process. The main goal of this work was to demonstrate the sensor’s ability to determine the soot particle number concentration of a test aerosol. This has been confirmed through a comparison with established laboratory instruments, like scanning mobility particle sizer or condensation particle counter. The observed size dependency of the laser induced incandescence sensor’s detection efficiency was successfully corrected with prior knowledge of the investigated particle size distribution. Furthermore, the sensor’s detection limit with respect to the particle diameter was determined to be well below 100 nm with a dependency on the applied laser power.