THz Time-Domain Spectroscopy

The setup for THz Time-Domain Spectroscopy (TDS) allows us to probe the optical properties of the sample under scrutiny at a few meV, hence, direct access to the electronic properties near the Fermi level can be achieved. The energy range covered by the setup is ≈0.5-3 THz, corresponding to ≈2-12 meV. This radiation is achieved by optical rectification of ultrashort laser pulses at 1.55 eV (800 nm) in a ZnTe crystal, and revealed in a second ZnTe crystal via Electro-Optical Sampling (EOS). OR makes available experiments in an energy region of the electromagnetic spectrum which is >100 times less energetic than the visible / near-IR range probed by the other setups available at T-ReX.

At present the setup works in transmission geometry. The reflection geometry, a cryostat and the pump-probe will be implemented in the near future.

The figure shows the electric field of the THz pulse under N₂ purging. The THz spectrum after inserting in the beam path a thin VTe₂ flake is also shown. The spectra corresponding to the two fields are reported. A clear absorption from the VTe₂ sample is evident. It is due to the IR absorption of a phonon mode at ≈1.58 THz; the right panel shows its lineshape in a ∝Transmission plot.