In his bachelor thesis entitled 'Thermooptischer Effekt in Öl-basierten Farbstofflösungen', Marlon conducted interferometry experiments to determine thermo-optical coefficients of solvents for dye media. The background of the investigation is that dye solutions are used for the thermalization of light and are thus also of interest for the generation of thermo-optical nonlinearities for photon gases within optical microresonators. Experimentally, Marlon observed the change of the refractive indices of different solvent samples upon controlled temperature increase in a self-designed sample holder for glass cuvettes that could be heated up to approx. 80°C. He found out that the themo-optical effect is more pronounced in oil-based solvents than in the commonly used solvent substances, such as ethylene glycol.
For his project „Hochauflösende Spektroskopie und Frequenzstabilisierung von optischen Quantengasen“, Darius performed experiments on the spectroscopy of Bose-Einstein condensates of photons. The aim of the work was to determine the wavelength of the condensates and to use the spectral information to actively stabilize the experimental setup. The background of such work is that the thermalization and Bose-Einstein condensation of photons occurs within a dye-filled optical microresonator whose geometric length determines the frequency of the condensates. Experimentally, Darius developed a spectrometer consisting of a high-resolution diffraction grating with 7GHz-resolution and realized active stabilization of the microresonator setup with down to 0.012nm precision, which is promising for future further investigations of optical quantum gases in periodic lattice structures.