A wideband coherent terahertz spectroscopy system using optical rectification and electro-optic sampling

We present a scheme for exploiting the nonresonant second-order nonlinearities in electro-optic media to extend the bandwidth of coherent spectroscopy in the far-infrared using ultrafast laser pulses. Using optical rectification and electro-optic sampling in 〈110〉 ZnTe for the generation and coherent detection of freely propagating THz radiation, respectively, we have demonstrated spectral sensitivity beyond 3 THz. This was accomplished by achieving phase matching for both optical rectification and electro-optic sampling over a broad range of THz frequencies.