No abstract

The paper presents theoretical and experimental results on photonic crystal structures which work under the self-collimation condition to couple free space waves into dielectric slabs in the sub-terahertz range. Using a standard machining process, two-dimensional photonic crystal structures consisting of a square array of air holes in the dielectric medium are fabricated. One of the structures has two adjacent parallel line-defects that improve the coupling efficiency. This leads to a combination of self-collimation and directional emission of electromagnetic waves. The experimental results are in good agreement with those of the Finite- Element-Method calculations. Experimentally we achieve a coupling efficiency of 63%.

A band pass filter based on hollow circular waveguide loaded with axially periodic dielectric and gold rings is demonstrated for THz frequencies. The presence of coaxial gold rings can introduce the single mode operation due to a high rejection values at the both-sides of pass-band, and an acceptable confinement for the proposed structure. The presented numerical results show that the influences of the gold rings on the propagation properties are significant.

No abstract