Modified spectral encoding for single-shot broadband terahertz detection based on cross-polarized wave

Achieving both high temporal resolution and a high signal-to-noise ratio (SNR) in single-shot terahertz (THz) coherent detection remains a significant challenge. In this work, we present an improved electro-optic sampling (EOS) technique for single-shot THz detection by employing a cross-polarized wave (XPW) pulse as the probe beam, instead of the conventional pulse. By employing a dual-BaF2 crystal configuration, the XPW process is enhanced, yielding a XPW pulse with an extended spectral bandwidth of more than two folds and significantly reduced spectral noise, making it very promising for the single-shot THz detection with high temporal resolution and a high SNR. Experimental results demonstrate the successful single-shot coherent detection of broadband THz radiation generated from the laser-irradiated metal wire using the proposed EOS method. The system achieves a detection bandwidth of 2.8 THz, with a maximum detectable frequency approaching 5 THz, along with a significantly improved SNR compared to conventional spectral encoding techniques.