Theuer, M.M.TheuerHarsha, S.S.S.S.HarshaGrischkowsky, D.D.Grischkowsky2022-03-042022-03-042010https://publica.fraunhofer.de/handle/publica/22381410.1063/1.35163072-s2.0-78751500931We report on a new coupling scheme for high resolution terahertz spectroscopy of microcrystalline films using parallel-plate waveguides. Metal flares are used to couple the terahertz radiation into and out of the waveguide. Very good coupling ratios as high as 35% at 1 THz from a collimated free-space beam into a subwavelength gap are obtained. This microwave approach is compared in terms of coupling ratio and spectral characteristics to the established technique of quasioptic coupling to parallel-plate waveguides using silicon lenses. Various samples at room and cryogenic temperatures are measured to show the capabilities of flare coupling for high resolution terahertz spectroscopy.en621530journal article