Components & Antennas
Components are developed here as answers to system-level constraints. A detector may be selected for room-temperature operation, a guided structure for access to a confined region, or an antenna and lens for controlled sub-terahertz radiation. The relevant performance is therefore not an isolated figure of merit: it is the effect of the component on bandwidth, coupling efficiency, spatial resolution, stability and integration.
Early work on wire-based probes used Sommerfeld-type modes to confine and collect the longitudinal electric field below the free-space diffraction scale. A passive structure demonstrated operation at 0.1 THz, while a related continuous-wave microscope reached a reported resolution of one thirty-third of the wavelength on a metallic test object. These experiments link electromagnetic mode engineering directly to a measurement function.
More recent activity includes photoconductive antenna architectures and a fully metallic geodesic Luneburg lens antenna developed through collaboration with KTH and ESA-ESTEC. Such projects should be presented as co-development and experimental research, with performance claims taken from the corresponding publications rather than inferred from the component name.
Antennas, detectors, bolometers, photoconductive devices, lenses, waveguides, and coupling structures for THz and sub-THz systems.
Components & Antennas across the measurement chain
The workflow can include requirement definition, instrument selection or development, calibration, acquisition, signal processing, reconstruction, and interpretation. The first decision is rarely the choice of an instrument. It is the identification of the physical quantity that could answer the research question: an interface delay, a spectral feature, a complex refractive index, a local field component, a surface profile, or a volumetric morphology.
Once that quantity is defined, source bandwidth, detector architecture, numerical aperture, scan geometry, dynamic range, sample environment, and reference measurements can be considered together. This system-level approach is particularly important in the terahertz range, where propagation loss, diffraction, atmospheric absorption, coherent artefacts, and material dispersion may all influence the same dataset.
Calibration, interpretation and validation
A capability is meaningful only when its limits are explicit. Work therefore asks which contrast mechanism is physically interpretable, what bandwidth and geometry are required, how repeatability is measured, and which independent method can serve as a reference. Reconstruction may improve access to phase, depth, or morphology, but it does not remove the need to test model assumptions and uncertainty.
Related publications
- Linear to radial polarization conversion in the THz domain using a passive system — DOI
The work presents a compact, passive device that transforms a conventional linearly polarized terahertz (THz) beam into a radially polarized one, a field configuration that offers superior focusing, enhanced longitudinal fields, and improved coupling to near‑field probes. By adapting a proven optical mode‑selection technique to the THz regime, the authors employ a circular metallic waveguide that supports only the fundamental TE11 and the radially polarized TM01 modes. A discontinuous phase element placed at the waveguide entrance inverts the polarization over half the beam, converting…
- Near-field wire-based passive probe antenna for the selective detection of the longitudinal electric field at terahertz frequencies — DOI
The work presents a novel passive probe antenna that can be operated at terahertz (0.1 THz) frequencies using a simple, purely passive structure. The antenna consists of a slender metal wire backed by a discontinuous phase plate that converts an ordinary linearly‑polarized free‑space beam into a radially polarized guided mode on the wire, with an estimated coupling efficiency of about forty percent. By exploiting the Sommerfeld wave that travels along the wire, the device can create a highly confined, longitudinal electric field at the…
- Continuous‐wave scanning terahertz near‐field microscope — DOI
The work reported by Guillet, Chusseau, Adam, Grosjean, Penarier, Baida and Charraut describes the development of a continuous‑wave terahertz (THz) near‑field microscope that exploits Sommerfeld surface waves guided along metallic wires. By combining differential phase plates, a Y‑splitter and a sharp, tapered needle probe, the authors created an imaging system that can be coupled to any linearly polarized THz source and detector. The key achievement is the demonstration of sub‑micrometre‑scale resolution—roughly a third of the probe tip radius, or about 10 µm—while retaining sensitivity…
- Coupling and Propagation of Sommerfeld Waves at 100 and 300 GHz — DOI
The study demonstrates that millimetre‑wave guided modes—known as Sommerfeld waves—can be efficiently launched and transported along simple metallic wires at 100 GHz and 300 GHz. By inserting a straightforward differential phase plate in front of the wire, the researchers achieved a theoretical coupling efficiency of about 32 percent, and confirmed experimentally a comparable value of roughly 23 percent. The wire acts as a low‑loss waveguide, with propagation losses measured at about 0.13 dB per metre for a 20 cm section, a figure that matches…
- Propagation beam consideration for 3D THz computed tomography — DOI
The study introduces a new physical model that captures the real behaviour of terahertz (THz) radiation when used for three-dimensional tomographic imaging. Unlike conventional X‑ray methods that treat the beam as a straight, uniform ray, the authors model the THz pulse as a Gaussian beam whose intensity spreads during propagation. This model is incorporated into a realistic acquisition simulator, allowing researchers to predict how the beam will illuminate an object from different angles and to produce more accurate projection data—sinograms—than those obtained with the…