In the Laboratory for Optical Diagnostic Methods and Renewable Energies (ODEE), we deal with the optical and laser spectroscopic analysis of reactive flows. We analyse exciting topics such as hydrogen or ammonia flames, catalytic systems or the combustion of iron. Using the Raman effect, it is possible to carry out simultaneous measurements of species concentration and temperature. A laser is focussed on a sample volume, the light scattered by the molecules is recorded by a spectrometer and processed further. One challenge of this measurement technique is the low signal intensity, particularly in the gas phase, which makes it susceptible to interference signals, such as those generated by thermal radiation during processes at high temperatures.
An interference-resistant Raman spectrometer (see left) has already been successfully developed and validated in previous work. In order to further improve this interference resistance, a so-called "Shfited Excitation" approach (SERDS) is being pursued. This should make it possible to identify interference signals in future experiments. For this purpose, two lasers with slightly different wavelengths are focussed alternately into the sample volume. This is to be realised using an optical Q-switch, a so-called Pockels cell. By applying a high voltage to a special crystal and using the polarisation of the laser light at high frequency, it is possible to switch back and forth between the two lasers.
The aim of this master's thesis is to further develop the existing laser excitation system so that both the second laser and the optical Q-switch can be integrated. To this end, a test setup is to be carried out in order to optimise the setting parameters of the Q-switch to our experimental specifications and to investigate the effects on the beam quality of the laser.
Beginn: Ab sofort
Betreuung durch: Nico Winkler, M.Sc.
