Quantum Engineering and Space Time Research - QUEST
A cornerstone of topical research in the Cluster of Excellence “Quantum Engineering and Space Time Research”, QUEST, is the research area “Enabling Technologies”, where the technological basement of the other three areas is subject of research. Within QUEST the technology area was established and consolidated by strategic investments and a new professorship in Applied Physics.
On the novel optics side the QUEST project Advanced Optical Materials was backed up with a new home-built coating facility (see figure 4) implementing a novel phase separated deposition process which aims at total optical losses of dielectric coatings systems below 0.1 ppm. Investigations in the control of deposition processes resulted in a comprehensive simulation of layer thickness deviations and accuracy in the atomic scale for certain layer designs. A variety of ternary oxide material combinations were studied before the back-ground of extensive models and improved beyond the former quality level in losses and power handling capability. Approaches for advanced process sensors and modeling techniques for the structural layer formation were investigated and resulted in the acquisition of complementary research projects involving industrial partners. The characterization infrastructure was adapted according to the objectives defined for the measurement of losses in the proposal, and additional damage threshold measurement facilities were established for the ns- and fs-pulse regime.
The main aspect of the optimization is based on a deeper understanding of the coating process and the film formation, but also the generation of coating conditions for lowest contaminations. Applying the novel plasma guiding approach, the spatial separation of material generation and deposition process is achieved. In this concept, the coating material is guided by a coaxial magnetic field and the direct line of view is masked by using a bent guiding coil. Consequently, only ionized deposition material of atomic scale can pass the guiding system and macro-particles are filtered. Applying this approach, coatings with equal particle density compared to the substrates were manufactured. For example, the optical scatter maps of the pure substrate and the dielectric stack including 73 layers are presented in figure 5. Obviously, a marginal increase in particle density was observed. A major parameter for the nucleation of the high quality films is the control of the coating material with respect to the kinematic properties as well as the specific composition of the adatoms. The concept of the phase separating IBS process allows controlling the species during the deposition process by varying the magnetic field strength of the guiding system. The manipulation of the energy distribution and the filtering of the material enable the possibility for novel concepts. Figure 6 displays the change of the lateral material distribution by tuning the current in the guiding coil. Applying this option, complex stacks including 71 layers were demonstrated.