Mirrors and output couplers for THz and optical radiation

Summary form only given. We use time-resolved THz spectroscopy in order to investigate the properties of highly conductive thin films. In this contribution we present experimental data on two of such film systems, which can be used in free-space THz radiation applications. We perform experiments on a thin indium tin oxide (ITO) film evaporated on a highly insulating glass substrate, in order to investigate its properties as a dichroic beamsplitter for THz and optical frequencies. In addition we study three different samples consisting of epitaxially grown p/sup +/-doped GaAs layers on GaAs substrates with different doping concentrations and layer thicknesses which are commonly used as contact layers in semiconductor devices (e.g. THz emitter structures).