Compact Terahertz Time-Domain Ellipsometer

Smart Farming Applications Enabled by a Compact Terahertz Time-Domain Ellipsometer

This project develops a next-generation terahertz (THz) time-domain ellipsometer featuring a compact, robust, and field-deployable design. By replacing the conventional Fourier Transform Infrared (FTIR) spectrometer architecture with advanced terahertz time-domain spectroscopy (THz-TDS) based on ultrafast short-pulse laser technology, the system enables broadband, high-precision ellipsometric measurements in the THz frequency range.

At the core of the measurement concept is the rotating polariser/sample/analyser (RPSA) ellipsometry principle, originally established for infrared and terahertz spectral ranges in pioneering work by the AG Gensch group at TU Berlin. The project introduces broadband spintronic terahertz emitters, whose polarisation plane can be electromagnetically rotated at kilohertz frequencies. These emitters function as ultra-fast rotating polarisers, enabling dynamic, high-sensitivity THz ellipsometric analysis without bulky mechanical components.

The AG Gensch at TU Berlin coordinates the project and contributes extensive expertise in THz time-domain spectroscopy, terahertz ellipsometry, and advanced RPSA measurement techniques. SENTECH Instruments uses its many years of experience to support the project development by defining precision-adjustment and calibration protocols and by contributing to the construction of the final demonstrator system.

A key innovation is the extension of the SENTECH SpectraRay Spectroscopic Ellipsometry Software platform into the terahertz spectral range. This includes the development of dedicated THz material models, a comprehensive material database, and adapted control architectures for next-generation THz components. The result is a fully integrated compact terahertz ellipsometer system optimised for advanced material characterisation and smart agricultural sensing applications.

By combining broadband THz spectroscopy, high-speed polarisation modulation, and advanced ellipsometric modelling, the project establishes a powerful new platform for non-destructive, contactless material analysis in the terahertz regime, opening new pathways for precision monitoring in smart farming and beyond.

Project Partner

TU Berlin – Chair of Terahertz and Laser Spectroscopy