Static and tunable devices for terahertz focusing and beam steering

The electromagnetic radiation with wavelengths between 0.1 and 1 mm, and frequencies between 0.3 and 3 THz, is usually called “terahertz radiation”. In this band, photons have energies in the milli-electronvolt range and interact with systems that have picosecond lifetimes and energetic transitions between 1.24 and 12.4 meV (Jepsen PU, Cooke DG, Koch M Laser Photonics Rev. https://doi.org/10.1002/lpor.201000011). Currently, numerous practical applications for optoelectronic THz systems are studied, but their progress has closely been linked to the more general development of a well-established technology. In this context, two different types of devices for THz-wave control will be presented: polymeric zone plates (ZPs) as THz lenses, and leaky-wave antennas (LWAs) based on nematic liquid crystals (LCs) for THz beam steering.