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A sub-terahertz vortex dielectric waveguide was designed and fabricated in the cyclic olefin copolymer (TOPAS) compound. The annular index profile was engineered using a holey cladding to support operation from approximately 200-300 GHz. The vortex waveguide was tested at 280 GHz using an OAM-endowed Laguerre-Gaussian mode generated by a stepped spiral phase plate.

A holey cladding dielectric waveguide with square cross section is designed, simulated, fabricated and characterized. The TOPAS waveguide is designed to be single mode across the broad frequency range of 180 GHz to 360 GHz as shown by finite-difference time domain simulation and to robustly support simultaneous TE and TM mode propagation. The square fiber geometry is realized by pulling through a heat distribution made square by appropriate furnace design. The transmitted mode profile is imaged using a vector network analyzer with a pinhole at the receiver module. Good agreement between the measured mode distribution and the calculated mode distribution is demonstrated.