Recordings of rare events require detection strategy in single-shot. It is also of crucial interest for recordings of terahertz waveforms in terahertz spectroscopy of irreversible processes. The time-domain spectroscopy usually requires scanning techniques that prevent the applications of very low repetition rate sources such as strong THz pulse sources based on table-top high power lasers or accelerators.
We present a strategy allowing complex electric fields to be recorded in single-shot using the chirped pulse electro-optic sampling technique at 1550 nm with signal processing techniques based on DEOS (Diversity Electro-Optic Sampling).
TeraFERMI is a beamline built up in 2015 at the Free Electron Laser (FEL) Fermi at Elettra in Trieste (Italy). Fermi is a seeded FEL that works in a single pass-single bunch mode at 10 or 50 Hz, covering the spectral range from 100 to 4 nm. TeraFERMI is based on a Coherent Transition Radiation source that provides high intense THz electric field in the MV/cm range. Such a THz electric field can push nonlinear materials well into their nonlinear regime. The beamline experimental setup fulfills the capability to address nonlinear regime by measuring both fluence-dependent transmission/reflection spectra and pump-probe response. A class of materials particularly studied at TeraFERMI is that of Topological Insulators. Indeed, thanks to their Dirac massless carriers of their conductive surface, topological insulators show nonlinear THz behavior similar to the case of graphene.