Use of the sol-gel process not only provides an alternative to traditional methods, but allows faster prototyping

cycles and production runs. Because the sol-gel provides both the photoactive component and substrate, film deposition

and patterning are consolidated into a single processing node. The post-bake develop solution removes unexposed

substrate to supplant the etch function. A sol-gel is a spin-on coating process in which film thickness and consistency is

controlled by chuck spin speed and the vapor evacuation rate of the chamber. A pre-exposure bake cycle sets or

stabilizes the material. This process has been employed in the manufacture of components in the past decade, notably by

Lumenon Innovative Lightwave Technology, Inc in the fabrication of integrated photonic devices in hybrid glass/polymer

circuits on silicon chips, and gracefully extends to devices on the THz scale. Figure 6 illustrates the sequence of

processes in fabricating two turns of helical geometry.

(a)

(b)

(c)

(d)

(e)

(f)

Figure 6. Fabrication of helical antenna elements (a) first wind is metal on transparent substrate (b) transparent layer on

first wind (c) contact metal through substrate to first wind (d) second wind (e) transparent layer on second wind (f)

contact metal through substrate to second wind.

3. ANTENNA SIMULATION

Simulation results for the 1 THz helical antenna are now presented to demonstrate electrical properties of the

antenna array, radiation pattern, and interference between array elements. Although the planar winding and contact

construction appear to be different from a circular helix, electrically it exhibits no difference. Simulation results verify

electrical equivalence. Additional windings to the helix enhance the gain, or equivalently, focus the radiation into a

smaller angular spread. The array of the helical elements is thus a THz lens or focusing element. With fabrication

process of the lens array in place, we demonstrate a layout of the antennas to obtain optimal constructive interference

between radiative elements.

λ/2

λ/2

Figure 7. Partial helical array shown in XY planar cross-section. Spacing between helix center points is λ/2, 150 µm for

the 1 THz model.