Terahertz spectroscopy and imaging up to 20 THz based on organic crystals

We present THz time-domain spectroscopy and imaging covering a wide frequency range up to 20 THz. Our approach uses highly efficient organic nonlinear optical crystals (DSTMS, OH1) and a compact femtosecond pump laser (1560 nm) with MHz repetition rate and ultrashort pulse width (<40 fs). By optimizing the optical geometry, we achieve high SNR (>80 dB at 4 THz, >70 dB at 10 THz). Our theoretical model agrees well with experiments. We validate our system by obtaining high-resolution THz spectra of water vapor and various solid substances. Additionally, we present THz imaging with sub-50 μm spatial and sub-10 fs temporal resolution.