2D TEM-mode THz quasioptics

Abstract

Scope of Study: The purpose of this study was to develop a two-dimensional wave guiding structure incorporating quasioptical mirrors, lenses, diffractive elements, sources and detectors for ultrafast pulses of THz radiation. Design curves allow rapid system development under various constraints. The theory governing the behavior of quasioptical components in the overall guiding structure is developed and first-order approximations are made for the effects of certain non-idealities expected in fabrication. Reflective, transmissive, and diffractive elements are demonstrated and analyzed. A new type of ultrafast source, adapted to the guiding structure has also been developed. A preliminary demonstration of guided-wave TEM-mode point-to-point communication using the new source is made.

Findings and Conclusions: Standard quasioptical techniques are found to be valid approximations for TEM-mode guided radiation for distances to several meters. The most significant issue in fabrication of integrated TEM-mode optics is found to be gaps between the elements and guide plates. Tilted mirrors may be used as mode converters within the waveguide. 2D integrated quasioptical mirrors, lenses, and slits were found to perform as expected for the analogous 3D device in unbounded space, as predicted. The new source was found to be a simple, powerful source in both free space and within the new guiding structure. The source was demonstrated to work as a useful THz source via photoconductive switching and optical rectification. Standard receivers were shown to work as detectors for the guided TEM-mode. In this work, the individual components of a point-to-point TEM-mode communication system for ultrafast pulses of THz radiation are demonstrated.