Abstract

Since the first demonstration of the electro-optic detection of coherent free space electromagnetic waves in 1996, this technique became a golden standard for the time-domain spectroscopy in the terahertz and mid-infrared frequency range. The detection principle is based on the Pockels effect leading to a terahertz (THz) electric field induced birefringence in the non-linear optical crystal. This birefringence is sensed by polarized near-infrared (NIR) light co-propagating with the THz wave. For a given non-linear crystal the detector sensitivity depends on the effective interaction length between THz and NIR waves. Therefore, the velocity mismatch between these waves is one of the essential problems of the electro-optic detection technique. It can be partially overcome by selecting a convenient combination of electro-optic (EO) crystal material and wavelength of the NIR probe light. A more general solution to this problem, independent on the crystal material and probe wavelength, has been recently introduced by us [1].

© 2011 Optical Society of America