Characteristics of the terahertz radiation from singlecrystals of N-substituted 2-methyl-4-nitroaniline

Abstract

Terahertz (THz) radiation was generated via optical rectificationfrom organic single crystals, i.e. N-substituted (N-benzyl,N-diphenylmethyl, and N-2-naphthylmethyl) derivatives of2-methyl-4-nitroaniline (MNA), and it was detected by means of theelectro-optic sampling method. The intensity and the spectrum ofthe THz radiation were compared with those of ZnTe and DAST(N, N-dimethylamino-N'-methylstilbazolium p-toluenesulphonate)crystals. The integrated intensity of the THz radiation from theN-benzyl-MNA crystal was two thirds of that for the ZnTe crystal,the best-known practical THz emitter, and was as intense as that forthe DAST crystal, the best organic THz emitter ever studied. Thespectrum of the ZnTe crystal extended to 3 THz, while that of theN-benzyl MNA and DAST crystals dropped off around 2.5 THz. The THzradiation intensities from all of the organic crystals were comparedquantitatively, on the basis of the consideration of moleculararrangements in the crystals. It was suggested that the absorptiondue to low-frequency phonon modes affected both the intensity andthe spectral band shape of the THz radiation.