A single-shot terahertz time-domain spectrometer using 1550 nm probe pulses and diversity electro-optic sampling

Classical terahertz spectroscopy usually requires the use of Fourier transform or Time-Domain Spectrometers. However, these classical techniques become impractical when using recent high peak power terahertz sources – based on intense lasers or accelerators – which operate at low repetition rate. We present and test the design of a novel Time-Domain Spectrometer (TDS), that is capable of recording a whole terahertz spectrum at each shot of the source, and that uses a 1550 nm probe fiber laser. Single-shot operation is obtained using chirped-pulse electro-optic sampling in Gallium Arsenide, and high bandwidth is obtained by using the recently introduced Diversity Electro-Optic Sampling (DEOS) method. We present the first real-time measurements of THz spectra at the TeraFERMI Coherent Transition Radiation source. The system achieves 4 THz bandwidth, and a 25 dB dynamic range. By reducing the required measurement time from minutes to a split-second, this strategy dramatically expands the application range of high power low-repetition rate THz sources.