Research overview
This paper presents a compact, high-efficiency terahertz time-domain generalized ellipsometer for characterising anisotropic materials, whose interaction with light changes its polarization state. Two fibre-coupled dual-channel photoconductive antennas act as source and detector, and a demultiplexing scheme captures four independent THz pulses in a single optical delay scan without any bulky or slow polarization optics during measurement. A one-off calibration, carried out with two high-extinction wire-grid polarizers at different azimuthal angles, corrects for polarization crosstalk in the emitter and detector. After calibration, a single measurement at one azimuthal angle was enough to determine the optical properties of a uniaxially birefringent a-cut sapphire (Al2O3) crystal, with the model matching the data in amplitude and phase. The approach reduces system complexity and opens the way to real-time, in situ THz polarimetric monitoring.
Key findings
- Generalized THz time-domain ellipsometry using dual-channel photoconductive emitter and detector
- Four independent THz pulses captured in a single optical delay scan
- One-off calibration with high-extinction wire-grid polarizers corrects polarization crosstalk
- Validated on a uniaxially birefringent a-cut sapphire (Al2O3) crystal
