This paper reports on the development of micromachined pillar arrays for the filtering of terahertz radiation. These pillar
arrays are fabricated using ultraviolet based processing of thick SU8. This micromachining technique enables the array
patterns, dimensions, and consequently the filter characteristics, to be readily defined. In particular, we demonstrate that
by combining individual filter arrays with either different periods or pillar diameters we can isolate individual pass bands
in the 1 to 2 THz region.
A plane-wave complex photonic bandstructure approach is used to calculate the pass bands as a function of rod diameter
for a system consisting of circular metallic rods in a 2-D square lattice. In addition, FDTD calculations are employed to
calculate the transmission properties of a finite 6-layer structure of the same form. The results of the two methods are
compared and found to be consistent. The effective plasma frequency, the lowest frequency at which propagation can
occur in the infinite lattice, is extracted from the bandstructure calculations, and is in the region of 1 THz for the 200 μm
period structures considered. The results for the effective plasma frequency are compared to those predicted by several
We report on the development of a surface micromachined process for the fabrication of coaxial apertures surrounded by periodic grooves. The process uses a combination of copper electroforming and the negative epoxy based resist, SU8, as a thin flexible substrate. The device dimensions are suitable for the implementation of filters at THz frequencies, and measurements show a pass band centred around 1.5 THz. These devices could form the basis of the next generation of THz biosensors.