Optical properties of DAST in the THz range.

We report the far-infrared properties of the organic crystal DAST, a popular terahertz emitter, from 0.6-12 THz through use of a THz spectrometer incorporating air-plasma THz generation and electro-optic (EO) sampling in a poled EO polymer. We identify absorption features at 1.1, 3.1, 5.2, 7.1, 8.4, 11, and 12.3 THz and at 1.1, 1.3, 1.6, 2.2, 3, 5.2, 7.2, 9.6 and 11.7 THz for a-axis and b-axis polarized THz radiation respectively. These results allow for more accurate prediction of the optimum crystal thickness for broadband THz emission via optical rectification and difference frequency generation.