Growth, transmission, Raman spectrum and THz generation of DAST crystal

The organic crystal 4-N, N-dimethylamino-4-N-methyl stilbazolium tosylate (DAST) was obtained by seed crystal method. We measured a maximum optical transmittance of 81%. Difference frequency generation (DFG) with reflecting double-pass optical parametric oscillator (OPO) was applied to generate terahertz (THz) wave. Tunable THz waves in the broad range of 0.51-19.69 THz were achieved. The maximum pulse energy was 267.7 nJ at 4.11 THz, and the laser-to-THz conversion efficiency of 1.04 x 10(-4) was obtained. Raman spectrum measurement also indicates the consistence of the Raman modes and the THz tuning curve from DAST crystal. The theoretical THz transmittance values are calculated and compared with the measured values. The variation tendency of the measured transmittance with THz frequency is found to be in agreement with that of the theoretical ones.