Highly efficient THz generation by optical rectification of mid-IR pulses in DAST

We report on efficient THz generation in DAST by optical rectification of intense mid-IR pulses centered at (i) 3.9 μm and (ii) its second harmonic 1.95 μm. Suppression multi-photon absorption shifts the onset saturation conversion efficiency to pump energy densities, which are almost an order magnitude higher as compared conventional schemes 1.5 Despite strong linear μm, exhibits a high optical-to-THz efficiency, we attribute resonantly enhanced nonlinearity advantageous phase matching velocity group driving pulse. At find that low combination with cascaded lead record efficiencies approaching 6%. The observed sensitivity parameters motivates in-depth study underlying interplay nonlinear wavelength- intensity-dependent effects.