Optical properties of Sr14-xCaxCu24O41 and Sr0.73CuO2

The optical reflectivity as a function of temperature of the title compounds has been measured over a broad spectral range from 4 meV up to 12 eV. On the one hand, our findings suggest a very anisotropic dynamics of the charge excitation spectrum when measuring along or perpendicular to the ladders in Sr14yxCa xCu24O41. On the other hand, the investigation of Sr0.73CuO2 allows us to study the electrodynamics of hole doped CuO2 chains alone without complications arising from the presence of Cu2O3 ladders in Sr14yxCa xCu24O41.