Subwavelength and microstructured planar THz waveguides, theory and   experiment
  Planar dielectric subwavelength waveguides are proposed as waveguides for THz radiation. The waveguide porous design maximizes the fraction of power guided in the air to avoid the complexity that all the materials are highly absorbent in the THz region. Convenient access to the mode region makes them also useful for sensing of biological and chemical specimens in the THz region. 
A. Markov, A. Mazhorova, B. Ung, H. Minamide, Y. Wang, H. Ito, and M.   Skorobogatiy
physics.optics