Author contributions F.F. carried out the simulation, experiments and evaluation, S.L. supported the device design, S.L. and S.R. helped interpreting the data, M.F. supplied assistance with the simulation, P.Y.A. carried out the experiments with half-sphere and prism. F.F., S.L., and S.R. devised the original concept. All authors jointly wrote the manuscript. Supplementary information has been submitted along with the main article. Correspondence to: Felix Fries, Sebastian Reineke Additional information 14