Terahertz-Wave Generation Using DFG/OR Methods in DAST Crystal with Irregular Morphology

Seed crystal method was used to grow organic nonlinear optical 4-N,N-dimethylamino-4-N-methyl stilbazolium tosylate (DAST) crystal in the present work and the crystal with curved faces was obtained. The morphology of the crystal were characterized and the formation reasons were discussed. Seed crystal plays an important role in the growth of crystal. Difference frequency generation (DFG) and optical-rectification (OR) methods were applied to generate terahertz (THz) waves from the crystal with irregular growth morphology. THz tuning ranges and the laser-to-terahertz conversion efficiency of the crystal were tested. Raman modes of crystals were used to reflect the positions of the absorption peaks and to study the origination of the absorption above 3.1 THz. The THz properties of the DAST crystal with curved surface were first characterized.