Terahertz-field-induced second-harmonic generation in a beta barium borate crystal and its application in terahertz detection

We report the observation of terahertz-field-induced second-harmonic (TFISH) generation in a beta barium borate (beta-BBO) crystal based on a four-wave-mixing process. Using the conventional second-harmonic generation in the beta-BBO crystal as a local oscillator, the crossed term between the TFISH and the local oscillator is proportional to the terahertz field. This phenomenon is used for coherent detection of intense terahertz waves, where a good linear response is observed for terahertz fields up to 160 kV/cm. In comparison, deviation from linear response and strong waveform distortion are observed when a 0.5-mm-thick ZnTe detector is used to characterize the same terahertz field. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3176439]