Terahertz Tomography
Terahertz tomography reconstructs internal structure from a set of measurements acquired over angle, depth or propagation geometry. Unlike a single two-dimensional image, the resulting volume depends explicitly on a forward model linking the object to the recorded field or intensity.
At terahertz wavelengths, diffraction, refraction and finite beam size can violate the straight-ray assumptions used in conventional computed tomography. Work in the portfolio has therefore addressed beam propagation, iterative transmission reconstruction, detector noise and post-reconstruction processing. These are not secondary corrections; they determine which structures can be recovered and how accurately their dimensions can be interpreted.
A real-time imaging system operating at 2.5 THz has been used to reconstruct complex objects and to derive further morphological information through segmentation, component labelling and skeletonization. This demonstrates a complete route from acquisition to structural metadata, while the validation remains specific to the objects, contrast and reconstruction conditions used in the study.
Acquisition and reconstruction methods for 3D terahertz imaging in transmission, reflection, and application-specific geometries.
Terahertz Tomography in the terahertz measurement chain
This technology forms one part of a larger measurement chain that includes sources, detectors, optics or antennas, positioning, acquisition, calibration, and data processing. Its value depends on how well those elements are matched to the sample and to the information that must be recovered.
Performance figures must therefore be read in context. Frequency range and bandwidth affect material contrast and depth resolution; aperture and working distance affect lateral resolution; dynamic range determines which weak interfaces remain measurable; and acquisition strategy controls speed, stability, and the amount of data available to a reconstruction algorithm.
Design constraints and performance limits
Propagation, coupling losses, coherent reflections, dispersion, alignment, and calibration can dominate an experiment even when the individual components perform well. Research on this technology combines modelling and measurement so that limitations are identified rather than hidden by post-processing. The final criterion is whether the recovered quantity remains reproducible and useful for the intended scientific or application question.
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…
- Theoretical and experimental studies of metallic grids absorption: Application to the design of a bolometer — DOI
The study delivers a comprehensive, validated framework for designing metallic grid absorbers with precisely tailored electrical resistivity, enabling the creation of efficient, room‑temperature bolometers and other thermal detectors. By treating structured metal layers as equivalent homogeneous films whose resistivity depends on geometry, the authors derived analytical expressions for transmission, reflection, and absorption that incorporate skin‑depth effects and diffraction when the grid period approaches the wavelength. Numerical simulations and experimental measurements at 0.3 THz and in the RF band confirm the model’s accuracy, demonstrating that…
- 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…
- 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…