Single-shot time-domain imaging of terahertz pulses via nonlinear optical frequency mixing

We demonstrate a single-shot temporal imaging technique for terahertz (THz) waves based on spatially resolved nonlinear frequency mixing. Using sum- or difference-frequency generation (SFG or DFG) in a non-collinear geometry, the temporal evolution of a THz field is mapped onto a spatially encoded near-infrared (NIR) signal. The angular separation of the generated NIR photons, governed by phase-matching conditions, enables direct imaging of THz temporal waveform on a camera without mechanical time-delay scanning. Using an intense THz source, the method achieves a signal-to-noise ratio (SNR) comparable to conventional electro-optical sampling techniques that rely on extensive temporal averaging. The approach does not require probe pulse chirping or monochromator signal isolation and provides access to both time- and frequency-domain information. These results pave the way for advanced THz diagnostics in experimental setups where scanning is impractical or real-time access is mandatory.