Single-shot ultrabroadband coherent detection of high-energy THz pulses

This paper presents a detector that captures the full electric-field waveform of millijoule-class terahertz pulses in a single laser shot. The pulses were generated by firing 5 J, 23 fs laser pulses at thin copper foils, a source that runs at a very low repetition rate, so conventional scanning measurements are impractical. The authors combine scanning-free solid-state biased coherent detection, using a thin silicon nitride film, with a non-collinear probe–THz geometry and balanced detection of two orthogonal polarizations. Together these suppress background and recover the THz field from one shot. The system resolved spectral content beyond 15 THz. The authors also analyse how polarization misalignment and other imbalances affect accuracy, and show how waveforms can still be recovered when the detection is imbalanced. Wire-grid linear polarizers set the THz polarization at the input of the detection system.