| With the demonstration of terahertz (THz) quantum cascade lasers over the past three years the THz community now has at its disposal a very compact, high power (in terms of THz technology), coherent source for system integration. This exciting technology requires the development of a number of new, compact, efficient components in order to integrate the technology into compact, portable systems. Such components include but are not limited to beam transformers, filters, polarizers, waveguides, and detectors. In this work photonic crystal structures are fabricated, tested and evaluated for their use in photonic-crystal-based THz components. For the 0.2 to 2.0 THz band, the feature size of photonic crystal structures is in the range of 30 mum to 200 mum, too small for the precision machining used at microwave frequencies and too large for most lithographic based processes commonly used for semiconductor processing. Here, for the first time, a rapid prototyping method using ThermoJetRTM printer is used to fabricate photonic crystal bandstop filters from 0.15 to 0.30 THz range and a combination of lithographic processes and bromine ion beam etching is used to fabricate 1.30 to 2.15 Thz transverse electric bandgap photonic crystal structures in a GaAs slab. Photonic crystal transmission spectra of the ThermoJetRTM fabricated devices were measured with a Bruker IFS 66v FT-IR interferometer. These devices exhibited photonic bandgaps (filter bandstops) at 0.17 THz and 0.23 THz along the Gamma-M direction for both the TM and TE polarized incident beams for devices with lattice constants of 0.787 mm and 0.586 mm, respectively, in agreement with the theoretical predication. Also for the first time, bromine-etched GaAs photonic crystal slabs were demonstrated using a direct detecting system employing an optically pumped molecular laser system. These structures were successfully characterized in range of 0.6 THz to 2.8 THz, where currently no tunable high power terahertz source is available. Finally, the work discusses the limitations of the current technologies, and how the technologies need to be improved in order to successfully apply photonic crystals to terahertz components. |
