Terahertz demonstrations of effectively two-dimensional photonic bandgap structures.

We demonstrate effectively two-dimensional (2D) terahertz (THz) photonic bandgap (PBG) structures for transverse electromagnetic (TEM) mode propagation within metal parallel plate waveguides (PPWG). The 2D-PBG structures consisting of square arrays of dielectric cylinders were characterized by THz time-domain spectroscopy (THz-TDS). THz photonic bandgaps were observed, as determined by the 160 mum lattice constant, the 65 mum diameter, and the dielectric constant of the cylinders. The experimental measurements were fitted with excellent agreement to 2D theory, confirming that for TEM mode propagation, effectively 2D propagation experiments can be achieved within the bounded space of the PPWG.