Characteristics of the terahertz radiation from single crystals ofN-substituted 2-methyl-4-nitroaniline

Abstract

Terahertz (THz) radiation was generated via optical rectification from organic single crystals, i.e. N-substituted (N-benzyl, N-diphenylmethyl, and N-2-naphthylmethyl) derivatives of 2-methyl-4-nitroaniline (MNA), and it was detected by means of the electro-optic sampling method. The intensity and the spectrum of the 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 the N-benzyl-MNA crystal was two thirds of that for the ZnTe crystal, the best-known practical THz emitter, and was as intense as that for the DAST crystal, the best organic THz emitter ever studied. The spectrum of the ZnTe crystal extended to 3 THz, while that of the N-benzyl MNA and DAST crystals dropped off around 2.5 THz. The THz radiation intensities from all of the organic crystals were compared quantitatively, on the basis of the consideration of molecular arrangements in the crystals. It was suggested that the absorption due to low-frequency phonon modes affected both the intensity and the spectral band shape of the THz radiation.

Investigation on rapid growth of 4-N,N-dimethylamino-4′-N′-methylstilbazolium p-toluenesulphonate (DAST) crystals by SNM technique

“…However, only a few of organic material could so far be crystallized in reasonable crystal size with high optical quality required for possible application. Organic crystals like N,N-dimethylamino-N 0 -methylstilbazolium p-toluenesulphonate (DAST), N-bezyl-2-methyl-4-nitroaniline (BNA) and 2-methyl-4-nitroanline (MNA) have very high NLO coefficients and at the same time have a low dielectric constant making them a perfect choice for THz generation [7,8]. Recent research proves that it is possible to synthesize stilbazolium derivatives such as 4-N,Ndimethylamino-4 0 -N 0 -methylstilbazolium 2,4,6-trimethylbenzenesulfonate (DSTMS) and trans-4 0 -(dimethylamino)-N-phenyl-4-stilbozolium hexafluorophospate (DAPSH) with very favorable crystal growth characteristics by carefully modifying the structure with various substitutions on the counter-anion and these materials are projected to be promising alternates for DAST, especially for THz generation [9,10].…”

Preparation, properties and structures of 1-methyl-4-{2-[4-(dimethylamino)phenyl]ethenyl}pyridinium crystals with various counter anions

“…Recently, organic crystals with large second-order nonlinear optical (NLO) properties have attracted attention for their efficient terahertz-wave generation [1,2]. Among them, 1-methyl-4-{2- [4-(dimethylamino)phenyl]ethenyl}-pyridinium p-toluenesulfonate (DAST: 2a in Fig.…”

Simultaneous reference and differential waveform acquisition in time-resolved terahertz spectroscopy

“…The laser output was split into three portions: a source beam for THz pulse generation, a pump beam for excitation of the sample and a gating beam for THz detection by free space electro-optic sampling. Terahertz waves were generated by optical rectification in 1.4 mm-thick [010] N-benzyl-2-methyl-4-nitroaniline (BNA) crystal [7,8]. BNA is an organic nonlinear crystal with high second order nonlinear coefficients [9] and allows a higher bandwidth of generated THz radiation than the most commonly used ZnTe.…”