Implementation of a Plenoptic Camera for Three-Dimensional Particle Detection in Plasma Crystals

Kurzfassung

For the first time, a plenoptic camera has been utilized to perform continuos capture of an extended 2D plasma crystal in order to study solid-state properties of the model system. With a commercial particle tracking software and custom-built analysis algorithms, investigations of the structure of the crystal have been undertaken, as well as dynamical studies of wave propagation within the crystal. The quality of the recomputed particle positions was shown to be sufficient for the structural analysis of the crystal and for the computation of the dispersion relations of acoustic (in-plane) phonons. However, for investigations of the out-of-plane dynamical particle behavior, the resolution of the depth coordinate was not satisfying over a wide range of experimental parameters. For large particle oscillations, in the so-called mode-coupling regime, parts of the optical dispersion relation branch could be imaged. This led to elaborate studies of mode-coupling between the longitudinal and out-of-plane modes. A strong inhomogeneity was found, confirming previous results obtained with another three-dimensional detection system. The findings gave valuable feedback about the anisotropy of mode coupling and are in accordance with theoretical discoveries that are not yet published. The plenoptic camera was proven to be an adequate detection system for plasma crystals as long as the particle oscillations are sufficiently large. Technical advances might lead to improvements in the depth resolution that would include a wider range of experimental parameters, such as stronger particle confinement. Future microgravity experiments at the DLR already consider the plenoptic camera as a possible detection system.