Terahertz waveguiding between parallel dielectric films

We report a study of terahertz waveguiding between parallel dielectric films, a system that can be viewed as a planar analogue of hollow core fibres that exploit anti-resonant reflection optical waveguiding (ARROW). With the aid of time domain waveguide mode imaging, the frequency dependent transition from ARROW to total internal reflection guiding in the individual films as the film separation is reduced and the effect on the transmission of adding variably spaced cladding layers are clearly revealed. Good agreement for the transmission, dispersion and loss is obtained with simple analytical models for film separations greater than about five wavelengths suggesting that the same models could be usefully used to predict the behaviour in the case of the technologically more important cylindrical geometry.